Preheat the oven to 350 degrees F. Line 2 baking sheets with parchment paper. 

In a bowl, mix together the flour, cocoa powder, baking powder, and salt. Set aside. 

In your mixer, beat together the butter and sugar until light and fluffy. 

Beat in the egg, then the cream cheese, followed by the vanilla and sauce. Mix until well-combined. 

Stir in the flour mixture just until there are no streaks of flour. 

Make balls of dough that are 1 ½ tablespoons big and then flatten. 

Bake for 8 - 9 minutes, then remove from the oven. Allow to rest on the baking sheet for one minute before transferring to a wire rack to cool. 

While the cookies are baking and cooling, make the frosting.

Beat the butter until creamy, then add in the powdered sugar and salt. Beat until well-combined. The mixture will look thick and very clumpy. 

Continue to mix as you drizzle in the vanilla and the cookies and cream sauce. The frosting should become smooth and creamy. Add more sauce as needed to get the desired consistency. Stir in half the crushed cookie wafers. 

Frost the cookies, then top with a sprinkling of the wafers on each cookie.