Preheat oven to 450 degrees F. In a large bowl stir together flour, cornmeal, baking powder, sugar, cream of tartar, salt, the 2 tablespoons green onion, and the sage. Using a pastry blender, cut in butter until mixture resembles coarse crumbs. Make a well in the center of the flour mixture. Add buttermilk all at once. Using a fork, stir just until moistened.
Turn dough out onto a lightly floured surface. Knead dough by folding and gently pressing it just until dough holds together. Pat or lightly roll dough until 3/4 inch thick. Cut dough with a floured 2 1/2-inch round cutter; reroll scraps as necessary. Dip cutter into flour between cuts.
Place dough rounds 1 inch apart on an ungreased baking sheet. Bake for 12 to 14 minutes or until golden. Remove biscuits from baking sheet. Cool slightly.
To serve, split biscuits and place on serving plates. Top with Sausage Gravy. If desired, top with additional green onions.
In a very large skillet cook bulk pork sausage and chopped onion over medium-high heat until meat is brown and onion is tender, using a wooden spoon to break up meat as it cooks. Do not drain.
Sprinkle all-purpose flour over meat mixture; stir into the meat mixture. Cook and stir over medium heat for 1 minute. While whisking, gradually add milk. Cook and stir until thickened and bubbly. Cook and stir for 1 minute more. Season with salt and pepper. Stir in snipped fresh thyme, if desired. Makes about 5 cups.
TO MAKE AHEAD:
Prepare biscuits as directed; cool completely. Place biscuits in a resealable plastic freezer bag; seal, label, and freeze for up to 2 months.
Prepare sausage gravy as directed. Place in an airtight container; seal and chill for up to 48 hours. To serve, thaw biscuits at room temperature (allow about 2 hours). If desired, preheat oven to 350 degrees F. Place biscuits on a baking sheet. Bake for 10 minutes. In a medium saucepan reheat sausage gravy over medium-low heat for 10 to 15 minutes or until heated through. If necessary, stir in additional milk to make desired consistency.