-
1
Preheat oven to 350 degrees.
-
2
Line 18 standard muffin cups with paper liners, or butter and dust with flour.
-
3
In a bowl, whisk the cocoa into the boiling water.
-
4
Let cool to lukewarm, then whisk in the buttermilk.
-
5
In another bowl, sift together the flour, baking soda, and salt.
-
6
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and sugars on medium speed until combined.
-
7
Add the eggs one at a time, beating well after each addition.
-
8
Add the vanilla along with the final egg.
-
9
Decrease the speed to low and add the dry ingredients in 3 additions alternately with the cocoa-buttermilk mixture in 2 additions, starting and ending with the dry ingredients.
-
10
Beat just until combined.
-
11
Divide the batter among the lined paper cups, filling each cup almost full.
-
12
Bake until the cupcakes are puffed and a toothpick inserted into the center of one comes out clean, 15-20 minutes.
-
13
Let cool completely on a wire rack.
-
14
Remove the cupcakes from the pans.
-
15
Spread a thick layer of frosting on each cupcake and serve.
-
16
To make the frosting: place the chocolate in the top of a double boiler over (not touching) barely simmering water, and warm, stirring often, until melted.
-
17
Remove from over the water and let cool to room temperature.
-
18
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and powdered sugar on medium speed until light and fluffy, about 3 minutes.
-
19
Beat in the vanilla.
-
20
Add the cooled chocolate and beat on low speed until incorporated, then increase the speed and beat until light and fluffy, about 2 minutes.
-
21
The frosting will keep for up to 3 days.
