1. Heat oil in a large nonstick skillet. Add the onion and apple; saute over medium heat, stirring occasionally, until softened, for about 3 minutes. Stir in the garlic, thyme, ginger and sage. Remove the skillet from the heat. Stir in the salt and pepper. Let the mixture cool to room temperature.
2. Mix together the apple mixture, sausage and egg white in a large bowl. Shape the mixture into 12 equal patties.
3. Wipe out the skillet with paper toweling. Working in batches if necessary, add the patties to the skillet. Cook over medium heat until browned and cooked through, about 3 to 4 minutes per side. Serve the patties on biscuits with a little coarse-ground mustard on the side if you wish.