Preheat oven to 425 F.
In a large bowl, sift together flour, baking powder, salt, baking soda and sugar.
Cut in butter-flavored shortening with a pastry cutter.
Grate in butter, tossing occasionally.
Stir in buttermilk until dough is wet and sticky.
Generously flour a work surface.
Turn dough out onto floured surface.
Sprinkle a little flour on the dough and your hands and begin to gently knead and fold the dough.
Add more flour as needed, but not too much, just enough so that the dough is manageable. Wet dough makes the best biscuits!
Fold the dough over several times.(This will create layers.)
Pat the dough out into a 1-inch thick rectangle.
Dip the biscuit cutter into flour and cut out the biscuits. (do not twist the cutter)
Place biscuits on pan, with the sides touching.
Brush tops of biscuits with a very light coating of mayonnaise.
Bake for 14 minutes or until tops are golden. (For a dark golden color, flip the oven to a low broil for the last 2 minutes. Be sure to keep your eyes on it at all times)
Remove from oven and brush with butter.