1. Put all dry ingredients into the bowl of a stand mixer with a paddle attachment. Turn the machine on low and blend for 15 seconds. Add the butter, margarine and buttermilk to flour mixture before turning mixer on. Turn mixer on low and count to 10. Do not overmix the dough. There will be large chunks of margarine, in the dough- that is a good thing.
2. Scrape dough from the bowl onto a floured tea towel and shape into a long vertical rectangle about 2 inches thick. The dough will seem rough and messy in the beginning. Using the edges of the towel, fold the lower part of the dough (about one-third) toward the center, then fold the top portion down. After folding in thirds, turn and repeat 7 times (roll, fold in thirds and turn).
3. After the eighth time of rolling, roll dough to 1-inch thickness. Using a 2-inch biscuit cutter, cut dough into rounds. Punch cutter into dough cleanly, without twisting. When refolding and rerolling the dough, gently stack it to retain the layers. Do not overwork.
4. Place biscuits on a baking sheet and freeze. Once they are frozen, transfer biscuits to plastic bags. The unbaked biscuits can be frozen for 2 months. To bake, heat oven to 350 degrees. Place frozen biscuits in the cups of muffin tins. (you do not have to grease- there is plenty of that already in the dough! Bake until golden brown, 23 to 25 minutes
For vegan biscuits – use almond milk and with 2 tablespoons of white vinegar to curdle it (does better if you do the day before) then replace butter and margarine with 4 sticks of vegan butter sticks.