For the Cookies:

1. In a small saucepan, combine chocolate and butter. Heat over low heat until both have melted. Stir until smooth and set aside.
2. In a small bowl, combine flour. Baking powder and salt. Set aside.
3. In a mixing bowl, beat together eggs, sugar and vanilla until mixture begins to thicken. Stir in cooled chocolate mixture followed by flour mixture.
4. Beat until combined. Let batter stand for 10 minutes in order to thicken up.
5. Preheat oven to 375°F.
6. Drop dough by tablespoon full about onto a lined baking sheet, keeping each cookie about 2 inches apart.
7. Bake for 8 minutes or until edges are set and cookies are slightly cracked.
8. Let cool for 1 minute before removing to a cooling rack.

For the Frosting Filling:

1. In a mixing bowl, combine butter and peanut butter beating until smooth.
2. Very slowly mix in powdered sugar, one cup at a time mixing well after each addition.
3. Add in milk and beat until frosting is spreadable consistency, adding more milk if necessary. Stir in mini chocolate chips.

To Assemble:

1. Pipe or spread a generous spoonful of frosting over the bottoms of 6 cookies.
2. Top each with remaining cookies.