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 vanillaextract
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)
Preheat oven to 325 degrees F (165 degrees C) and place the oven rack in the center of the oven. Line the bottom and sides of an 8 inch (20 cm) square pan with aluminum foil. (The aluminum foil should hang about two inches (5 cm) over the sides of the pan to make it easy to lift the brownies from the pan.)
In a small saucepan melt the butter (can also melt the butter in the microwave). Remove from heat and pour into a large heatproof bowl. Stir (or whisk) in the sugar and cocoa powder. Whisk in the vanilla extract and eggs, one at a time, mixing until the batter is nice and shiny.
In a small bowl, whisk together the flour, baking powder, and salt. Fold this flour mixture into the batter. Finally, fold in the sour cream and chocolate chips.
Pour into the prepared pan and smooth the top. Bake for about 28 – 30 minutes, or until a toothpick inserted into the center has moist crumbs clinging to it. Remove from oven and place on a wire rack to cool to room temperature. Then, to make the brownies easier to cut, cover and place in the refrigerator for two hours or until firm. When ready to cut the brownies, lift the aluminum foil out of the pan and, with a sharp knife, cut the brownies.