Preheat oven to 350°F. Line a 12-count cupcake tin with cupcake wrappers or spray the wells with a nonstick baking spray.
In the bowl of a stand mixer fitted with the paddle attachment, beat together the butter and sugar until light and fluffy. Add in the eggs one at a time; mixing in between each addition. Mix in the vanilla. Set aside.
3 tablespoons unsalted butter, 1 cup granulated sugar, 2 large eggs, ½ teaspoon pure vanilla extract
In another medium bowl, whisk together the flour, baking soda, baking powder, cocoa powder, and salt.
1 cup all-purpose flour, ¼ teaspoon baking soda, 1½ teaspoons baking powder, ½ cup unsweetened cocoa powder, ¼ teaspoon kosher salt
Alternate adding the dry ingredients and the milk to the butter mixture. Pour half of the flour mixture, followed by half of the milk, mixing until combined after each addition. Repeat with remaining flour mixture and milk, and mix until everything is combined.
¾ cup milk
Scoop batter into each of the cupcake liners, filling about ⅔ of the way full. Bake for 17-18 minutes, until a toothpick inserted into the middle comes out clean. Cool completely before moving onto the filling.