Combine the dry ingredients: In the bowl of the food processor, add the flour, sugar, baking powder, baking soda, and salt. Pulse a few times to mix.
Add the butter: Scatter the cold cubed butter over the flour mixture. Pulse in short bursts—about 8 to 10 times—until the mixture resembles coarse crumbs. Be careful not to over-process; visible small bits of butter are what you want.
Add liquids: Pour in the cold buttermilk and the yeast mixture. Pulse just until the dough starts to come together and form clumps.
Roll the dough and cut the biscuits: Turn out onto a floured surface and knead gently a few times until it comes together. Roll the dough to 1 inch thick and cut using a 2 to 2 1/2-inch round cutter. Place the biscuits close together in a 10-inch skillet or on a parchment-lined baking sheet.
Let rise: Cover with a towel and let them rise in a warm place for 1 hour. Preheat oven to 400°F. Brush the tops with cream or melted butter.
Bake: Transfer to the oven and bake for 10 to 12 minutes or until golden brown.