1. In the bowl of a heavy-duty electric stand mixer, whisk flour, sugar, cocoa, salt and baking powder.
2. Add butter 1 tbsp. at a time, beating at medium speed after each addition, until just blended.
3. Add egg yolks one at a time, mixing until blended (dough will be sandy and somewhat loose but will hold together when squeezed between your fingers). 
4. Divide the shaggy dough between 2 sheets of parchment paper; squeeze and knead each pile until it holds together. Shape each half into a rough disc shape.
5. Place another piece of parchment on top of each dough ball; using a rolling pin, quickly roll out dough to less than ¼" but no less than ⅛" thick. Transfer both sheets of dough (between parchment) into the refrigerator; chill for 1 hr.
6. Remove top sheet of parchment from the dough rounds. Cut dough with 2" round cookie cutters, rerolling scraps. Place cutouts 1" apart on parchment-lined baking sheets; transfer to the refrigerator for 30 min. to chill completely.
7. Preheat oven to 350°.
8. Bake in preheated oven until edges are lightly browned (about 12 min.), rotating and turning pans halfway through.
9. Remove from oven; let cookies rest on sheet pans for 2 min., then transfer to a wire rack to cool.
10. In a large, clean mixing bowl, whip frosting with a hand mixer until very soft and spreadable.
11. Add crushed candy and a few drops of food coloring; whip until very fluffy and lightly pink.
12. When cookies are completely cool, fill pairs of cookies with frosting. Store at room temperature, loosely covered, for up to 5 days.

Find It!

• Find Kowalski's Signature Classic Buttercream Frosting in the Cake Case.