Whisk together the cornstarch with water until smooth, and combine with vegetable broth, garlic, onion salt, black pepper, thyme, basil, and parsley in a saucepan over medium-low heat. Bring the gravy mixture to a simmer, and cook and stir until gravy is hot and thickened, about 5 minutes.
Heat vegetable oil in a large skillet or wok, and stir-fry the carrot, red pepper, broccoli, and snow peas over medium-high heat for 2 to 3 minutes, until just tender. Stir in the tofu, mushrooms, and baby corn, and stir and cook about 1 more minute, until mixture is heated through.
Pour the gravy over the vegetables and tofu, stir to combine, and serve hot.