Slice beef into strips. Combine all ingredients except brown rice, green onions, and cornstarch in the instant pot. Add 1 cup water. Lock lid. Set valve to sealing. Program for manual-high and 20 minutes. Combine cornstarch and 3 tablespoons water. Stir into instant pot. Cook on sauté 2-3 minutes to thicken the sauce. Serve beef mixture over cooked brown rice. Top with green onions and more sesame seeds, if desired.