10 tablespoons (140 grams) unsalted butter

1 1/4 cups (250 grams) granulated white sugar

3/4 cup (75 grams) unsweetened cocoa powder, preferably Dutch processed

1 teaspoon pure vanilla extract

2 large eggs, room temperature

1/2 cup (65 grams) all-purpose flour

1/4 teaspoon baking powder

1/4 teaspoon salt

1/4 cup (60 ml) sour cream (full or reduced fat)

1/2 cup (85 grams) semi sweet or bittersweet chocolate chips (optional)