buttermilk bisquits

How to make the best buttermilk biscuits

1 c. Bread flour,
1 c. durum/semolina flour,
1/2 tsp. Baking soda,
1&1/2 tsp. Baking powder,
1 tsp. Salt,
1/4 c. unsalted butter,
3/4 c. buttermilk.

I was in error- set oven to 400 and the convection will go to 375 20 minutes