Cookies & Cream Cake

I was at my parents house last week and I was watching the Food Network and saw this cake being made. That night while we were all deciding what to have for dinner, we decided to make this cake. Melissa was the one that baked and frosted it for us.
-Brenda
Cake
2 cups all-purpose flour
3/4 cup unsweetened cocoa
2 cups granulated sugar
1 1/2 tsp baking powder
1/2 tsp baking soda
1 teaspoon kosher salt
3 large eggs, plus 1 egg yolk
1 cup unsalted butter, melted
1 cup buttermilk (I use 1 tablespoon lemon juice and then enough milk to equal 1 cup)
1 1/2 cups crushed chocolate sandwich cookies

Cookies & Cream Cheese Icing
1 stick butter, softened
2 (8-ounce) packages cream cheese, softened
pinch salt
1 tsp vanilla extract
3 3/4 cup confectioners sugar
1 1/2 cups crushed chocolate sandwich cookies

In a large bowl combine flour, cocoa, sugar, baking powder, baking soda & salt. Add the eggs and egg yolk one at at time while mixing with a hand-held mixer. Beat until well mixed, then add the melted butter and combine. Add the buttermilk and beat until smooth, about 2-3 minutes. Add in the crushed cookies and beat until incorporated.

Pour evenly into 2 9-inch round, greased and floured cake pans and bake in a 350 degree oven for 30-35 minutes or until done. Cool on wire rack for 5 minutes, then take the cake out of the pans and cool completely.

For the Icing:
In a large bowl, blend the butter and cream cheese until smooth. Add the salt and vanilla. Add in the confectioner's sugar, 1/2 cup at a time, until smooth. Beat in the crumbled cookies.

Frost the cake once it is cooled completely.