1/2 cup unsalted butter, set out and bring to room temperature
1/2 cup granulated sugar
1/2 cup brown sugar
1 teaspoon vanilla extract
1 1/2 cups all purpose flour
1/4 cup unsweetened cocoa powder
1/2 teaspoon baking soda
1/2 teaspoon baking powder
1/2 teaspoon salt
1/2 cup milk-chocolate chips
Heat oven to 350 degrees. Cream the butter and sugars in a large bowl with an electric mixer on high speed. Reduce to medium speed and add the egg and vanilla.
In a medium bowl, sift together the flour, cocoa, baking soda, baking powder and salt. Slowly add the dry mixture to the butter mixture. Mix until well blended. Fold in the chocolate chips.
Spray two cooking sheets with non-stick cooking spray or cover with parchment paper. Form the dough into approximately 1 1/2-inch balls. Place on cookie sheets, approximately 2 inches apart.
Bake until the centers are just set, about 12 minutes. Let cool on sheets for 5 minutes, then transfer to wire racks.