Yield: 12 small or 6 large biscuits.
2 cups all-purpose flour
2 teaspoons baking powder
1 teaspoon baking soda
1 teaspoon sugar
1 teaspoon salt
1 cup whole buttermilk, chilled
8 tablespoons unsalted butter, melted and slightly cooled, plus more for brushing
Preheat oven to 425°. Line a rimmed baking sheet with parchment paper and lightly grease with cooking spray.
In a large bowl, whisk together flour, baking powder, baking soda, sugar, and salt. In a small bowl, stir together chilled buttermilk and melted butter. The mixture will look curdled. Use a rubber spatula to stir the buttermilk mixture into the flour mixture just until the ingredients are incorporated and the mixture slightly pulls away from the edges of the bowl.
Using a greased ¼-cup measure, portion the dough and drop biscuits onto the prepared baking sheet, spacing each about 1½ inches apart.
Bake biscuits until tops are golden brown, 13 to 15 minutes. Remove from oven and brush with additional melted butter. Serve warm.