Heat up oil in a wok/pan. Saute onions and garlic. Add the frozen seafood mix. Cover the wok to cook thaw and cook the mix at the same time.
Add the green beans then stir in the soy sauce and black pepper. Continue cooking until green beans have softened a bit. Maintain the crunchiness of the green beans. Turn the heat off then stir in the cornstarch mix to thicken the sauce.