In a large bowl, whisk together flour, sugar, baking powder, salt, baking soda and yeast.
2 ½ cups all purpose flour, 3 tablespoons granulated sugar, 1 teaspoon baking powder, 1 teaspoon kosher salt, ½ teaspoon baking soda, 2 ¼ teaspoons instant yeast
Cut in the butter and shortening using a pastry knife or work it in with your hands just until pea sized pieces of butter remain.
4 tablespoons unsalted butter, ¼ cup shortening
Add the buttermilk and stir just until combined.
1 cup buttermilk
Transfer the dough to a well floured surface and pat it out into a square that's about 1 inch thick. Fold the square in half and pat it out again. Rotate the dough and fold in half again and pat out again until 1 inch thick.
Use a 2 or 2 ¼ inch biscuit cutter, dipped in flour, to cut out the biscuits. Don't twist the biscuit cutter, just push down and pull up.
Place biscuits on a parchment lined baking sheet or cast iron skillet and cover with plastic wrap or a light towel. Let rest for 30 to 60 minutes.
Preheat oven to 425°F. Brush melted butter on the top of the biscuits and bake for 15 to 20 minutes or until golden brown and cooked through. Brush the hot biscuits with additional melted butter and serve immediately.
3 tablespoons unsalted butter