Preheat oven to 350. Lightly spray a baking sheet with cooking spray. Cream together butter and powdered sugar. Mix in cocoa powder. Add egg yolks and vanilla and mix well.
In a separate bowl whisk together flour, baking powder, and salt. Gradually mix dry ingredients into wet ingredients until just combined. Roll 1-1.5 tablespoons of dough into a ball and place on greased baking sheet. Repeat with remaining dough placing dough balls 2 inches apart.
Use the back of a wooden spoon to press a small well into the center of each dough ball. Bake 10-12 minutes. Use back of wooden to re-form well in each cookie. Allow to cool on wire racks.
Place chocolate chips in a microwave-safe bowl and microwave on half heat for 1 minute. Stir, and microwave 20 seconds at a time, until melted. Spoon about 1 teaspoon of melted chocolate into the center of each cookie. Allow to cool mostly before gently pressing peanut butter cups into the chocolate centers.
Allow to cool completely. Warm peanut butter in microwave about 20-30 seconds until pourable. Drizzle peanut butter over cookies in any pattern you like. Store in airtight container.