Bloom yeast in water; stir to dissolve.
In a large mixing bowl, combine flour, baking powder, baking soda and salt.
Cut in butter and shortening with a fork or pastry cutter.
In a separate bowl, combine bloomed yeast and water mixture with buttermilk.
Make a well in the center of the flour mixture.
Pour buttermilk into center of well.
Slowly incorporate flour into liquid a little at a time (I prefer a wooden spoon). Don't grab too much of the flour at once. The trick is to slowly mix together in a fluid motion to incorporate as smooth as possible, with as little agitation to the dough as you can.
Once incorporated, turn onto a lightly floured board or counter. Pat down into a large rectangle about 1” thick. Carefully fold about a third of the dough into the center. Fold the other third from the other side into the center. Pat down again and repeat.
Cut into desired size using a floured cutter.
Place onto lightly greased pan, or a parchment lined pan without spray works best.
Preheat oven to 425°.
Cover loosely with plastic wrap and allow to sit at room temperature for about 20-30 minutes.
Bake for about 10 to 12 minutes depending on size of biscuit. They should be puffy, soft and deep golden brown.