Add the remaining 2 tablespoons of oil to the wok and swirl to coat. Add the remaining half of the garlic and stir-fry for 30 seconds. Add the bell pepper, corn and scallions and stir-fry until crisp-tender, 2 to 3 minutes. Stir the sauce mixture and add to the wok. Stir-fry until the sauce thickens, about 2 minutes. Return the beef and scallops to the wok, stir to coat, then stir in the basil. Transfer to a platter and serve.