For the Vanilla Cupcakes: 

1. Preheat: Preheat oven to 400°F. 
2. Egg Prep: If eggs are not room temperature, add whole eggs into a bowl with warm water and let sit for 5-10 minutes. Crack eggs into a separate bowl, and set aside. Doing this gives you a chance to fish out any unwanted egg shells!
3. Melt Butter: In a microwave-safe bowl, microwave the butter at 15-30 second intervals until completely melted. Set aside until ready to incorporate into the recipe.
4. Wet Ingredients: Measure sour cream and milk into a small, microwave-safe bowl. Microwave for 30 seconds to bring to room temperature and set aside.
5. Dry Ingredients: Add the all purpose flour, granulated sugar, box cake mix, and salt to a large mixing bowl. Use a whisk or spoon to gently combine the ingredients until they are evenly distributed.
6. One Bowl: Combine all ingredients into the larger bowl containing the dry ingredients. Don’t forget to add the vegetable oil and vanilla extract (or imitation vanilla)!
7. Mix It Up! Mix ingredients together with an electric hand mixer

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   , starting on low and increasing speed to med-high. Scraping bowl periodically to make sure all ingredients are incorporating and not sticking to the bottom of the bowl. Mix until batter is smooth and fluffy, usually 1-2 minutes!
8. Let Batter Rest: Set batter aside to rest for 15 minutes.
9. Prep Cupcake Pan: Prepare the cupcake pan by lining with cupcake liners while the batter is resting.
10. Fill Em Up! Fill each cupcake liner 2/3 full with cake batter.
11. Bake: Bake at 400°F for 5 minutes, then lower oven temperature to 350°F for 7-8 minutes. Use a toothpick insert into the center of a cupcake – if it comes out clean or with a few moist crumbs, it’s good to go. You can also gently press your finger into the top of one of the cupcakes, if it springs back slowly, it’s done!
12. Cooling: Cool in pan for 5 minutes, and transfer cupcakes to a wire cooling rack to finish cooling.

For the Buttercream Frosting: 

1. Whip It Up! Start by adding the room temperature butter to a stand mixer, fitted with the paddle attachment. Whip the butter on a medium speed for about 1-2 minutes, scraping the sides and bottom of the bowl at least once.
2. Vanilla & Salt: Add 2 tablespoons of heavy cream or milk to the butter, along with the vanilla extract and salt.
3. Start Mixing! Turn mixer on medium speed until these ingredients are incorporated. This should only take about 30 seconds. Again, scrape that bowl.
4. Powdered Sugar: Lower mixer speed to the lowest setting and start adding the powdered sugar in increments. Adding a tablespoon of heavy cream or milk between each.
5. Mix on Low: Slightly increase the mixer speed to help mix these ingredients, but do not turn on too high or you will whip too much air into the buttercream.
6. Scrape, Scrape, Scrape: Remember to scrape the sides and bottom of the mixing bowl to make sure all of the ingredients are incorporated.
7. White Gel Food Coloring

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   : After adding all powered sugar and heavy cream, finish by adding 2 teaspoons of white gel food coloring

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   . (This step is optional, and only necessary if you want a bright white buttercream)
8. Finish: Mix on low-medium until all ingredients are incorporated, at this point you should have perfectly white, smooth and fluffy buttercream frosting!