- 2 1/2 cups unbleached all purpose flour
- 2 tablespoons sugar
- 1 tablespoon baking powder
- 3/4 teaspoon cream of tartar
- 1/2 teaspoon salt
- 7 tablespoons chilled unsalted butter, cut into 1/2-inch pieces
- 1 cup (packed) coarsely grated sharp cheddar cheese, chilled
- 1/2 cup coarsely crumbled Stilton cheese (about 2 ounces), chilled
- 1 1/4 cups chilled buttermilk
- 1 large egg
- Position 1 rack in bottom third and 1 rack in top third of oven and preheat to 400°F. Butter and flour 2 large baking sheets. Whisk first 5 ingredients in large bowl to blend well. Add butter and rub in with fingertips until mixture resembles coarse meal. Add both cheeses; rub in with fingertips until cheeses are reduced to small pieces. Blend buttermilk and egg in small bowl. Add to flour mixture, stirring just until dough is evenly moistened.
- Using 1/3 cup dough for each biscuit, drop 6 mounds onto each prepared sheet, spacing 2 to 3 inches apart. Bake biscuits 10 minutes. Reverse positions of sheets. Bake biscuits until golden brown and tester inserted into center comes out clean, about 10 minutes longer. Place biscuits in basket; serve warm.