In a large mixing bowl, beat together the butter and the sugars until light and fluffy.
Add vanilla and eggs and beat again.
Melt the baking chocolate in a small bowl in the microwave in 30 second intervals, stirring between each interval, until chocolate is smooth and fully melted.
Add the melted chocolate to the butter mixture and mix again.
Sift together flour, baking powder, and cocoa powder, and add to the butter mixture. Mix until fully incorporated.
Fold in chocolate chips.
Chill for 30 minutes.
Using a rounded tablespoon to scoop out the dough and shape into balls.
Place on a greased cookie sheet 2 inches apart. Bake at 350° for 5 minutes. Remove from oven. Press one peppermint patty onto each cookie, and bake for another 4-5 minutes. Allow to cool on the cookie sheet for 5 minutes before transferring to a cooling rack.