Heat vegetable oil in a large frying pan over medium-high heat. Add brown onion and garlic. Cook, stirring, for 3 minutes or until onion has softened. Add mince. Cook, stirring with a wooden spoon to break up mince, for 8 to 10 minutes or until browned and cooked through.
Add flour. Cook, stirring, for 1 minute. Add teriyaki sauce, vinegar, sesame oil and sugar. Reduce heat to medium-low. Cook, stirring occasionally, for 5 minutes or until sauce thickens. Add snow peas and green onion. Cook for 2 minutes or until snow peas are tender. Sprinkle with sesame seeds. Serve with rice.