Preheat your oven to 350° F and line your baking sheets with parchment paper.
In a large bowl, add your melted butter and peanut butter and stir until combined. Then, add brown sugar and sugar and mix until well combined.
Add your eggs and vanilla extract and mix until light and fluffy.
Add in your cocoa powder, flour, cornstarch, baking soda, and salt. Stir until combined.
Scoop your cookie dough into 1-2 inch balls and place on your baking sheets lined with parchment paper and few inches from each other. (To prevent them from spreading together)
Bake at 350° for 8-10 minutes. Remove from oven.
Using a round cookie cutter or glass, scoot the edges of your cookies to make them round.
Using the back of a measuring spoon, make a well in the middle of your cookie and fill it with muddy buddies.
Sprinkle a dusting of powdered sugar on your cookies.
Share and enjoy!!