Ingredients

4 tablespoons (1/2 stick) unsalted butter, melted, plus more for pan 

1/4 cup unsweetened cocoa powder, plus more for pan 

3/4 cup all-purpose flour, (spooned and leveled) 

1 teaspoon ground ginger 

1 teaspoon pumpkin-pie spice 

1/2 teaspoon baking soda 

1/2 cup packed dark-brown sugar 

1/4 cup unsulfured molasses 

1 large egg 

1/4 cup sour cream 

1/2 cup semisweet chocolate chips 

Confectioners' sugar, for dusting (optional) 

Preparation

Preheat oven to 350 degrees. Butter an 8-inch square baking pan. Line bottom with a strip of parchment paper, leaving an overhang on two sides; butter paper. Dust paper and sides of pan with cocoa; set aside. In a medium bowl, whisk together cocoa, flour, ginger, pumpkin-pie spice, and baking soda; set aside.

In a large bowl, whisk together butter, brown sugar, molasses, egg, and sour cream until smooth. Add flour mixture; stir just until moistened (do not overmix). Stir in chocolate chips. Transfer batter to prepared pan; smooth top.

Bake until a toothpick inserted in center comes out clean, 30 to 35 minutes. Transfer to a wire rack; let cool completely. Using paper overhang, lift gingerbread from pan. Transfer to a cutting board, and cut into 16 squares. Before serving, dust bars with confectioners sugar, if desired.