This was adapted from Smitten Kitchen who adapted from Gourmet.
1 1/2 cups all-purpose flour
2 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
2 tablespoons cold unsalted butter, cut into bits
1/4 pound sharp Cheddar cheese, coarsely grated (about 1 1/2 cups)
1 cup sour cream
Preheat oven to 425°F. Whisk together the flour, baking powder, baking soda and salt in a large bowl. Cut butter pieces in with two knives. Stir in the cheddar and sour cream until the mixture forms a sticky dough. Pat it out to a circle, 1/2-inch thickness on a very well-floured counter. Cut into wedges. Bake on a parchment lined baking sheet for 15 to 17 minutes, until golden on top.
Sourcream & Cheddar Biscuits printable version.