Fudgy Brownie Cake with Chocolate Fudge Frosting

ByBrittany
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This fudgy brownie cake with chocolate fudge frosting is the ultimate chocolate lover’s dream dessert. It has all the rich, fudgygoodness of brownies – baked into an easy layer cake. The brownie cake layers start with a box brownie mix, so this recipe is nearly fail-proof in my opinion. Perfect for birthdays, celebrations, or anytime you want a super chocolatey dessert that looks impressive but still super easy to make!

A slice of rich brownie cake with layered textures, adorned with a decorative chocolate swirl, sits on a white plate.

WHY YOU’LL LOVE THIS RECIPE

  • Brownies + Cake = Perfection: Everything you love about brownies, but in a sliceable fudgy layer cake.
  • Easy & Stress-Free: Starts with a box brownie mix, so no measuring flour, sugar, or leavening agents.
  • Ultra-Fudgy: Rich and chocolatey in every bite, and never dry or crumbly.
  • Crowd-Pleaser: Both kids and adults will love this fudgy goodness.
  • Perfect for Any Occasion: Great for birthdays, holidays, or anytime you need a chocolate dessert.
A close-up of a rich brownie cake with a piece cut out, resting on a white plate alongside a black fork. Crumbs scattered.

INGREDIENTS FOR THIS CHOCOLATE BROWNIE CAKE

  • Brownie Box Mix: Flour, cocoa, sugar, and leavening – all built in. It delivers the perfect brownie cake base, with room to add ingredients that take it to the next level.
  • Salted Butter: For the brownie cake, melted butter adds richness and that classic buttery flavor, while keeping the cake super fudgy.
  • Eggs:  Eggs provide structure and help the brownies hold together, while the extra yolk adds even more richness and moisture. This combination is what gives these brownies that chewy-yet-dense texture that keeps them from being cakey or dry!
  • Water: Water helps bring the batter together, ensuring it’s smooth and spreadable. It also slightly loosens the mix so the brownies bake evenly without being too thick and dense.
  • Chocolate Chips: Chocolate chips add little pockets of melty chocolate throughout the brownie cake layers. They create extra texture and flavor in every bite.

INGREDIENTS FOR THE CHOCOLATE FUDGE FROSTING

  • Unsalted Butter: Room temperature butter is needed for the base of the chocolate fudge frosting.
  • Vanilla Extract + Salt: Balances flavor and sweetness.
  • Powdered Sugar: The sugar base of the chocolate fudge frosting – it adds sweetness and helps create that smooth, fluffy texture that’s perfect for spreading or piping.
  • Unsweetened Cocoa Powder: Cocoa powder adds rich chocolate flavor and deep color to the frosting. It helps create that classic fudge taste without making the frosting overly sweet.
  • Melted Chocolate Chips: Melted chocolate chips bumps regular chocolate frosting to a rich and delicious chocolate fudge frosting. I like using semi-sweet chocolate chips for this!
  • Heavy Whipping Cream: Heavy cream helps make the buttercream extra smooth, creamy, and easy to spread—it also adds a little richness and can be used to adjust the consistency.
Close-up of a slice of rich brownie cake on a white plate, partially forked and crumbled, showcasing its fudgy texture.

TIPS FOR FUDGY BROWNIE CAKE LAYERS 

Brownie cake layers bake a little differently than traditional cake layers, so don’t worry – this texture is supposed to be rich and dense! These tips will help you achieve the perfect texture – without overthinking it.

  • Stir, Don’t Whip. Mix until everything’s just combined. Over-mixing sneaks in too much air and gives you cake-y brownie layers (and we’re not here for that).
  • Chocolate on Chocolate. Fold in chocolate chips for melty pockets in every bite.
  • Don’t Over-Bake: The number one secret to a fudgy brownie cake is pulling it out at the right time. The edges should look set, but the center can still look slightly soft. If you wait until the middle looks fully baked like a regular cake, the layers will turn dry instead of fudgy.
  • Toothpick Trick. Unlike traditional cakes, you don’t want a completely clean toothpick. A few moist crumbs are perfect. Wet batter = needs more time. Totally dry = likely over-baked. Bake until a toothpick comes out with a few fudgy crumbs, not completely clean—that’s when you know they’re just right.
  • Don’t Panic! Brownie cakes continue cooking from residual heat after coming out of the oven. The centers may look a little soft or gooey, but they will firm up as they cool. This is what gives that dense, chewy brownie texture instead of a dry cake crumb.
  • Let Them Cool! Let them cool at least 30-45 minutes before cutting. As the layers cool, the structure sets and the texture becomes perfectly fudgy & sliceable.
  • Chill for Extra Clean Layers: If your layers feel very soft, pop them in the fridge for 20–30 minutes before frosting. This helps them firm up and makes stacking much easier.
  • Right Pan Size: Spreading the batter too thin can lead to dry layers. Using the recommended pan size keeps the brownie cake layers thick and fudgy.

MORE CHOCOLATE RECIPES TO TRY:

A close-up of a rich, gooey brownie with chocolate chips, partially on a black fork, set against a white plate.

HOW TO ASSEMBLE THE BROWNIE LAYER CAKE

1. Cool completely

Make sure the brownie cake layers are completely cooled before assembling. Since they’re fudgy and dense, cooling helps them firm up, which makes stacking much easier and prevents sliding.

2. secure the first layer

Spread a small dab of frosting onto the center of your cake board using an offset spatula or knife — this helps keep the cake in place.

3. add frosting between layers

Set the first brownie cake layer down, then spread an even layer of chocolate fudge frosting over the top. Repeat this process until all of your brownie cake layers are stacked!

4. frost the outside

Next, add a thicker coat of chocolate frosting around the sides of the cake, using a bench scraper to smooth everything out. For this cake, I left the top unfrosted so the crackly brownie top could show – this shows the signature look of a brownie for this brownie cake!

5. decorate (optional)

For the design shown, use a piping bag fitted with a #888 piping tip and pipe frosting around the top edge. I also used plain brownie pieces from these m&m brownies to garnish and add a fun decorative touch.

6. chill for clean slices

For extra clean slices, chill the cake for 15–20 minutes before serving.

A fudgy brownie cake topped with decorative chocolate frosting swirls and chunks of brownie, set on a white plate.

Well, that’s it – the best chocolate brownie cake recipe for all you brownie lovers! A fail-proof, easy, delicious brownie cake — the kind of recipe people don’t stop asking about. Whether you need a brownie birthday cake, a chocolate fix, or simply because you’re in the mood for a good piece of cake, this recipe delivers every time!

Continue below for the easy-to-follow recipe, dig in, and enjoy every bite!

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A slice of rich brownie cake with layered textures, adorned with a decorative chocolate swirl, sits on a white plate.

Fudgy Brownie Cake with Chocolate Fudge Frosting

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  • Author: Brittany
  • Total Time: 2 hours
  • Yield: 25 slices 1x
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Description

This fudgy brownie cake with chocolate fudge frosting is the ultimate chocolate lover’s dream dessert. It has all the rich, fudgygoodness of brownies – baked into an easy layer cake. The brownie cake layers start with a box brownie mix, so this recipe is nearly fail-proof in my opinion.

Ingredients

Units Scale

Brownie Cake Layers:

  • 1 Box Brownie Mix (see notes)
  • 1/2 Cup Salted Butter (melted)
  • 2 Eggs
  • 1/4 Cup Water
  • 1 Cup Chocolate Chips

Chocolate Fudge Frosting: 

  • 7 1/2 cups Powdered Sugar (2 lb bag)
  • 1 cup Unsalted Butter (room temperature)
  • 1 Teaspoon Vanilla Extract
  • 1/2 Teaspoon Salt
  • 1/2 cup Unsweetened Cocoa Powder
  • 1 cup Semi-Sweet Chocolate Chips (melted)
  • 1/2 – 3/4 cup Heavy Whipping Cream or Milk

Instructions

For the Brownie Cake Layers:

  1. Preheat & Prep: Preheat oven to 325°F. Prepare (3) 6 inch cake pans or (2) 8 inch cake pans with baking spray or a homemade pan release. You can also use parchment paper rounds at the bottom of the pans for extra insurance.
  2. Melt Butter: In a microwave-safe bowl, microwave the butter at 15-30 second intervals until completely melted. Set aside.

  3. Combine the Ingredients: In a large mixing bowl, add the brownie mix, eggs, melted butter, and water. Stir until the batter is almost combined—don’t over-mix.

  4. Chocolate Chips: Add the chocolate chips to the brownie batter and gently fold them in with a spatula until evenly distributed.

  5. Scoop into Pans: Scoop batter into prepared cake pans. If you can, use a food scale

    (affiliate)

    to evenly distribute batter between pans for consistent cake layer size. For thinner cake layers, use the (3) 6 inch pans. For thicker cake layers, use the (2) 8 inch pans. 

  6. Bake: Bake for 26-28 min for 6 inch pans, and 30-32 min for 8 inch pans. Check periodically as all ovens bake differently! 
  7. Cooling: Let brownie cake layers cool completely in the pans. 
  8. Storage: Double wrap your cake layers in plastic wrap and freeze for up to 3 months. When you’re ready to decorate, simply take out and frost straight from frozen—no need to thaw!

For the Chocolate Fudge Frosting:

  1. Whip the Butter: Start by adding the room temperature butter to a stand mixer, fitted with the paddle attachment. Mix the butter on medium-high for 30 seconds-1 minute, scraping the sides of the bowl at least once during this time.
  2. Vanilla & Salt: Add the vanilla extract and salt.
  3. Start Heavy Cream: Add 2 tablespoons of heavy cream or milk and continue mixing until incorporated. Scrape the bowl.
  4. Melt Chocolate Chips: Melt the chocolate chips in a microwave-safe bowl, stirring every 20–30 seconds until smooth, then set aside.
  5. Powdered Sugar: Lower mixer speed to the lowest setting, and start adding the powdered sugar in 1-2 cup increments. Add a tablespoon of heavy cream or milk between each.
  6. Mix It Up! Slightly increase the mixer speed to help blend these ingredients, but do not turn on too high or you will whip too much air into the buttercream.
  7. Cocoa Powder: Add the unsweetened cocoa powder.
  8. Reminder: Scrape the sides and bottom of the mixing bowl to make sure all of ingredients are incorporated and to avoid any clumps of butter or powdered sugar.
  9. Add Melted Chocolate Chips: Add the melted chocolate chips into the chocolate buttercream.
  10. Last Step: Mix on low-medium until all ingredients are incorporated, this could take a few minutes. At this point you should have perfectly smooth, chocolate fudge frosting!

Equipment

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Notes

Brownie Mix: My favorite brownie mix is Duncan Hines-Dark Chocolate Fudge (18.2 oz).

For a stiffer buttercream, add less than recommended amount of heavy cream.

For ultra-creamy buttercream, add a max of 12 tablespoons of heavy cream.

Cake Sizing: This brownie cake was baked in (3) 5 inch pans (and half the recipe) – so my sizing and thickness of layers are different. I understand the most common cake pan sizes are 6 & 8 inch, which this recipe works perfectly for as well! 

  • Prep Time: 15 minutes
  • Cook Time: 30 minutes + 1 hour of cooling
  • Category: Dessert
  • Method: Baking
  • Cuisine: American

Did you make this recipe?

Share a photo and tag @coveandkitchen — I can’t wait to see what you’ve made!

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