Step 1

Preheat the oven to 350, and line 4 cups in a muffin pan with paper liners.

Step 2

In a medium-sized bowl, whisk together the flour, cocoa, baking soda, baking powder, and espresso powder (if using).

Step 3

Next, in a small measuring cup, whisk together the buttermilk, oil, vanilla and brown sugar very well.

Step 4

Add the wet to the dry, and stir until just mixed.

Step 5

Divide between the cupcake liners and bake for 16-17 minutes. They're done when the tops spring back when touched (if you under-bake, they'll sink).

Step 6

Let cupcakes cool completely.

Step 7

In a small bowl, beat together with an electric mixer on HIGH the butter, powdered sugar, heavy cream, and vanilla. Beat for 1 minute, until very fluffy and light.

Step 8

Finally, stir in the cookies by hand, crushing them as you add them. (I went a little light on the cookies so the frosting was more photogenic, but the frosting tastes best when you add all 4 cookies).

Step 9

Frost the cooled cupcakes with the frosting and serve.