Whisk sifted 2 cups all-purpose flour, sifted , 1/2 tsp baking soda, 4 tsp baking powder, or 1 tbsp + 1 tsp, 1/2 tsp salt and 2 tsp granulated sugar together in large bowl.
Using a pastry blender or a fork, cut in 1/4 cup unsalted butter, cold and cut into pieces and 1/4 cup shortening, cold and cut into pieces until crumbly.
Add 2/3 cup sour milk or buttermilk and stir just until combined, do not over mix.
Using both hands that have been floured, gently knead dough in the bowl to form a large ball of dough (kneading 6-8 times).
Turn out onto floured surface and roll about 1/2” thick. Using 2 ¼-2 ½” round cutter, cut into biscuits. Do not completely re-roll scrapped dough, instead, press together to form another circle of dough and continue cutting.
Place biscuits on either a greased baking sheet or greased round 10” or 12” cast iron skillet.
Bake at 450°F for 10 minutes, or until golden on top.
Brush hot biscuits with melted butter immediately after removing from oven. Serve warm.