Preheat oven to 450 degrees. In a large bowl, combine flour, baking soda, baking powder and salt. Using a pastry cutter (I just use my hands) cut the butter into the flour mixture until it resembles coarse sand.

Stir in the buttermilk, scallions and parsley until just combined. Do not over mix. Dough may still be slightly sticky.

Turn dough onto a floured work surface. Gently pat the dough out to 1/2 inch thick. Fold the dough over 3 or 4 times and pat it down again to about 3/4 inch thick.

Cut out biscuits using a round cutter or glass. Press out dough scraps to cut additional biscuits.

Place biscuits on a lightly greased baking sheet and bake for 10-12 minutes, or until golden brown.

Meanwhile, make the gravy by heating olive oil in a large skillet over medium high heat. Add the scallion whites and sauté them for about 1 minute, or until tender.

Add the sausage, breaking it up with a wooden spoon as it cooks. Cook for 8-10 minutes, or until sausage is no longer pink.

Add the butter to the skillet and stir until melted. Stir in the flour and cook for a few minutes more. Stir in the milk and cream and bring to simmer. When the gravy has thickened, stir in the cayenne, salt and pepper.

Serve gravy over sliced biscuits. Garnish with parsley if desired.