Preheat oven to 350 and line two baking sheets with parchment paper.
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and both sugars until light and fluffy. Add the vanilla, then the eggs, 1 at a time, and mix well. Add the cocoa and mix again.
Sift together the flour, baking powder, baking soda and salt and add to the chocolate with the mixer on low speed until just combined.
Using a two ounce (1 3/4") ice cream scoop, or a rounded tablespoon, drop mounds of dough on the prepared baking sheets. You are going to bake these without adding the candy corn at first. Bake for 11-12 minutes, then pull the cookies out. Have the candy corn ready to stick into the cookies - I like three per cookie. Gently press them into the soft dough, then return to bake for 2 more minutes exactly. Pull the cookies out, and cool on a wire rack.
Notes
This recipe is based on the Barefoot Contessa Chocolate White Chocolate Chip Cookies. After testing several versions, I found it only works to add the candy corn at the very end. Trust me! This would also be an amazing recipe to use with peanut butter chips...