Preheat oven to 450 degrees F.
In a large mixing bowl, whisk together flour, baking powder, baking soda, and salt.
2 cups all-purpose flour, 4 teaspoons baking powder, 1/4 teaspoon baking soda, 3/4 teaspoon salt
Using a pastry blender or your fingertips, quickly cut shortening and butter into flour mixture until combined until you have various sizes no larger than peas. This should also take less than a minute.
2 Tablespoons salted or unsalted butter, 2 Tablespoons shortening
Make a well in the center of the flour and pour in the buttermilk.
1 cup cold buttermilk
Working from the outside in, bring the flour into the center with a large spoon, scooping and turning bowl until the buttermilk is incorporated into the flour. (Use a light hand here, we are simply gently tossing the flour together with the buttermilk until it's combined)
Turn the wet sticky dough out onto a well-floured surface. Keep a small pile of extra flour on hand to add to your surface or your hands as needed.
Flour your hands and bring the dough together, then lightly fold it in half in a gentle kneading motion.
Do this about 5-7 times until your dough comes together and is beginning to feel smooth.
Pat dough out to about an inch thick.
Using a floured cutter, cut the dough into desired sizes.
Turn biscuits upside down and place onto an ungreased baking sheet, close together but not touching.
Brush tops with a little buttermilk
extra buttermilk for brushing tops
Bake until they have risen nice and tall and are golden brown on top, about 15 minutes. Serve warm.