Line a muffin tin with cupcake liners and set aside.
In a medium bowl, sift together flour, cocoa powder, baking soda, and salt.
1 1/3 Cups All-Purpose Flour, 1/2 Cup Natural Unsweetened Cocoa Powder, 3/4 teaspoon Baking Soda, 1/4 teaspoon Salt
Set aside.
In the bowl of an electric mixer fitted with the paddle attachment, beat together butter and sugar on medium speed until light and fluffy, about 3 minutes.
1 Stick Buter, 1 Cup Granulated Sugar
Scrape down the sides and bottom of the bowl as necessary.
Beat in eggs, one at a time, beating well after each addition.
2 Large Eggs
Beat in vanilla extract.
1 teaspoon Pure Vanilla Extract
With the mixer on low speed, add half of the flour mixture and beat just until combined.
Beat in milk until combined, followed by the other half of the flour mixture.
1/2 Cup Whole Milk
Add hot water and beat just until combined. Do not overmix—the less you mix, the lighter the cake will be.
1/2 Cup Hot Water
Divide batter evenly between cups, filling them about 3/4 full.
Bake for 15-20 minutes, or until a toothpick inserted into the center comes out clean or with just a few moist crumbs.
Allow cupcakes to sit for 10 minutes, then remove from pan and allow to cool completely on a wire rack.
For the frosting:
In the bowl of an electric mixer fitted with the paddle attachment, beat butter at medium speed until pale and fluffy, about 2 minutes.
1 1/3 Sticks Unsalted Butter
Add powdered sugar in 2 additions, beating well after each addition, until mixture is completely smooth and sugar has dissolved into the butter.
3/4 Cup Powdered Sugar
Add vanilla extract and melted chocolate and beat until combined.
1/2 teaspoon Pure Vanilla Extract, 1/2 Cup Milk Chocolate
Beat in additional powdered sugar as necessary until frosting is spreadable.
Add a pinch of salt if you’d like to cut the sweetness.
Pinch Salt
Keep beating until shiny, fluffy, and smooth.
Use frosting immediately to frost cupcakes, or store in the fridge, covered, for up to 3 days.
Before using, bring to room temperature and whisk until smooth.
Cupcakes are best the same day they’re made, but can be kept in an airtight container at room temperature for up to 3 days.
Unfrosted cupcakes can be kept in the freezer for up to 2 months.
Thaw them on the counter or overnight in the fridge.