Preheat & Prepare Pan
Preheat your oven to 350°F (about 175‑180°C). Lightly spray a 9‑inch pie plate (or similar pan) with non‑stick spray.

Mix Wet Ingredients
Mix the melted butter, brown sugar, and granulated sugar together in a large bowl until well combined.

Cool Slightly & Add Egg + Vanilla
Let that mixture cool for about 5 minutes (this prevents scrambling the eggs). Then beat in the egg, the two yolks, and vanilla.

Add Dry Ingredients
Stir in flour, cornstarch, and salt. Mix just until they come together — overmixing will make the cake tough.

Fold in Candy
Gently fold the chopped candy into the dough. It will be thick and chunky.

Bake
Spread the mixture in the prepared pan. Smooth the top. Bake for about 35 minutes or until the edges are set, top is golden‑brown, and the center is only slightly jiggly.

Cool Before Frosting
Transfer the cake to a wire rack. Let cool for at least one hour. If it’s warm, the frosting will melt or slide off.

Make Chocolate Frosting

• Sift together confectioners’ sugar and cocoa powder to remove lumps.

• Using a mixer, beat the soft butter until creamy (≈ 2 minutes).

• On low speed, slowly add the sugar/cocoa mixture alternating with heavy cream.

• Add vanilla and salt. Increase speed to high and beat until light and fluffy (another 1‑2 minutes).

Frost & Decorate
Use a piping bag (open star tip works great) to decorate the cooled cookie cake. Add extra chopped candy on top, if desired.

Slice & Serve
Slice into wedges and enjoy!