Preheat oven to 350F. Line two baking sheets with a silicone reusable baking sheet or parchment paper.
In a small mixing bowl, combine the flour, baking soda, baking powder, and salt. Whisk to aerate and combine all ingredients. Set aside.
In a large bowl with an electric mixer, beat the butter and peanut butter together until smooth and well incorporated.
Add the sugars (brown and granulated) to the butter mixture and mix for 2-3 minutes until the mixture appears light and fluffy.
Add the egg and vanilla, mix until combined. Add in milk and mix once more.
Slowly add the flour mixture to the butter mixture and beat until just combined.
In a small bowl, mix together cocoa powder and powdered sugar.
Using your hand or a medium cookie scoop, portion out approximately 2 tbsp of cookie dough. Roll into balls and roll in your cocoa topping.
Place rolled cookies onto baking sheet, allowing room for the cookies to spread out while baking (2 inches between cookies).
Bake for 10-14 minutes or until chocolate coating begins to crack and edges are firm to the touch.
Keep your cookies on their cookie sheet for 5-10 minutes to cool. Then, once firm enough to lift, transfer them onto a wire rack to cool completely.