Bring bourbon to a boil in a small saucepan; remove from heat. Add chocolate chips, stirring until smooth.
Lightly spoon flour into dry measuring cups, and level with a knife. Combine the flour, cocoa, baking powder, and salt, stirring with a whisk.
Combine sugar and butter in a large bowl; beat with a mixer at medium speed until well combined. Add vanilla and eggs; beat well. Add flour mixture and bourbon mixture to sugar mixture, beating at low speed just until combined.
Spread batter into a 9-inch square baking pan coated with cooking spray. Bake at 350° for 25 minutes or until a wooden pick inserted in the center comes out clean. Cool in pan on wire rack.