Stir the cornstarch, stock, soy sauce and sesame oil in a small bowl until the mixture is smooth.
Heat 1 tablespoon vegetable oil in a 12-inch skillet over medium-high heat. Add the shrimp and stir-fry until they're cooked through. Remove the shrimp from the skillet.
Heat the remaining vegetable oil in the skillet. Add the vegetables, ginger and garlic powder and stir-fry until the vegetables are tender-crisp.
Stir the cornstarch mixture in the skillet. Cook and stir until the mixture boils and thickens. Return the shrimp to the skillet and cook until the mixture is hot and bubbling. Serve over the rice.
