(Skip this step if using pre-made homemade Kung Pao Sauce
) While baking the Brussels sprouts, prep and cook the Kung Pao sauce. Mix Chinkiang vinegar, soy sauce, sugar, cornstarch and salt in a small bowl. Add oil and Sichuan peppercorns in a big pan, and cook until hot. When the peppercorns turn dark brown, scoop out and discard. Add dried red chili pepper. Stir until the peppers turn dark brown. Add minced garlic and ginger. Stir a few times. Stir the vinegar based sauce to dissolve the cornstarch completely; add to the pan. Cook until the sauce thickens and remove from the stove immediately.