Make the gravy: Spray an ice cube tray with canola oil, and set aside In a large cast-iron skillet, saute onion in olive oil over medium-high heat. Add ground sausage and cook until golden. Once done, sprinkle with flour and stir until grease from sausage thickens. Stir in milk. Add gelatin, then add thyme, sage, salt, pepper and cayenne.Fill the ice cube tray with gravy, and refrigerate for 30 minutes.Assemble the biscuits: Preheat the oven to 350 degrees, and line a baking sheet with parchment paper.Split the 8 biscuits in half and place on the prepared baking sheet. Place a prepared stuffing cube on the middle of each biscuit, and cover each with the other half of biscuits. Seal each biscuit completely by pinching around the edges.Brush each biscuit with egg wash, top with freshly ground pepper and bake for 12 to 15 minutes until golden. Serve immediately.