01 - Prepare all vegetables and optional protein as directed.
02 - Heat a large skillet or wok over medium-high heat. Add 1 teaspoon vegetable oil, then sauté garlic and ginger until fragrant, about 30 seconds.
03 - Add cabbage, carrots, mushrooms, and scallions. Stir-fry for 2-3 minutes until just softened.
04 - Add bean sprouts, soy sauce, sesame oil, oyster sauce (if using), and white pepper. Stir-fry for 1-2 minutes more.
05 - Stir in optional protein if using. Transfer filling to a tray to cool completely.
06 - Place a spring roll wrapper on a clean surface with a corner facing you. Spoon 2 tablespoons filling near the bottom corner. Fold the bottom corner over the filling, then fold in the sides and roll tightly. Seal the edge with cornstarch slurry. Repeat with remaining wrappers and filling.
07 - Heat 2 inches vegetable oil in a deep pan to 350°F.
08 - Fry rolls in batches, turning occasionally, until golden and crisp, about 3-4 minutes. Drain on paper towels.
09 - Serve hot with sweet chili sauce, soy sauce, or your favorite dip.