2¼ teaspoons active dry yeast (1 envelope)
½ cup warm water (100-110°)
2 cups buttermilk
5½ cups all-purpose flour
1½ tablespoons baking powder
1½ teaspoons salt
½ teaspoon baking soda
¼ cup sugar
¾ cup shortening
2 pounds thinly sliced cooked ham
Dijon mustard for serving, optional
Combine the yeast and water in a 4 cup liquid measuring cup and allow to stand for 5 minutes. Stir in the buttermilk.
In a large bowl, combine the flour, baking powder, salt, baking soda and sugar. Using your fingers or a pastry blender, cut the shortening into the flour mixture. Add the buttermilk mixture and stir with a fork just until moistened.
Turn the dough out onto a well-floured surface and knead four to five times. Roll the dough to ½-inch thickness and cut into squares. Alternately, you can use a 2-inch round cutter. Place onto baking sheets lined with parchment or a nonstick baking mat.
Cover and allow to rise in warm place for about 1 hour. They will not double.
Bake at 425º for about 10 minutes, until golden. Cool slightly, then split each biscuit and stuff with ham. If desired, spread biscuit tops with Dijon mustard.