2 1/2 C flour
4 tsp sugar
1 tsp salt
1 tsp baking powder
1/2 tsp baking soda
6 T unsalted butter, cut into small pieces and chilled
1 1 /2 C whipping cream
1/4 C sour cream
Stir together flour, sugar, salt, baking powder and soda in a mixer with paddle attachment. Add the butter an mix until consistency of course crumbs. Add the whipping cream and sour cream and mix until just combined. The dough will b slightly wet and sticky. Cover the bowl with plastic wrap and chill until dough is firm and cold, at least 1 hour and up to 4.
Preheat oven to 425. Lightly butter heavy baking sheet. When biscuit dough is chilled, turn out onto a floured surface and knead gently 3-4 times, then press into a 6×9 inch rectangle 1 inch thick. Cut into 6 squares, brush tops with cream and sprinkle lightly with sugar. Bake 17-20 minutes until puffed and lightly browned.