Ingredients
1/2 cup unsalted butter, at room temperature
1/2 cup granulated sugar
1/2 cup brown sugar
1 large egg
1 teaspoon pure 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
1/2 cup semisweet chocolate chips
Step 1
Heat oven to 350°F. Cream the butter and sugars in a large bowl with an electric mixer on high speed. Lower to medium speed and add the egg and vanilla. Sift together the flour, cocoa, baking soda, baking powder, and salt. On low speed, add the dry mixture to the butter mixture. Beat until fully incorporated. Fold in the chocolate chips.
Step 2
Form the dough into approximately 1 1/2-inch balls. Place on parchment- or foil-lined baking sheets, 2 inches apart.
Step 3
Bake until the centers are just set, about 12 minutes. Let cool on sheets for 5 minutes, then transfer to wire racks.