Drizzle another 1 tablespoon oil into the hot skillet. Add the onion and stir-fry until spotty brown, 1 to 1-1/2 minutes. Add the Tender Vegetables and stir-fry until crisp-tender, 1 to 1-1/2 minutes longer. Make a well in the middle of the skillet and add the remaining 1 tablespoon oil, garlic, and ginger and cook until fragrant, a few seconds, then stir-fry into the vegetables. Return the steamed Firm Vegetables and the Protein to the skillet and stir-fry to heat through. Add the Flavoring Sauce and cook to coat all the ingredients. Stir the cornstarch mixture and add it to the skillet. Cook until the juices become saucy and glossy. Serve immediately.