Slice your beef thinly against the grain. In a medium bowl, combine the sliced beef with soy sauce, cornstarch, and sugar. Let marinate for 10 minutes.

While the beef marinates, whisk together the oyster sauce, a bit of water or broth, sesame oil, and cornstarch in a small bowl until smooth.

Heat vegetable oil in a large wok over medium-high heat. Add minced garlic, stirring for 30 seconds until fragrant.

Add the marinated beef to the hot wok and stir-fry for about 2 minutes until lightly browned and cooked through.

Add your choice of vegetables, pour in the prepared sauce, and stir continuously for 3-5 minutes until the sauce thickens.

Remove from heat and serve hot over steamed rice or noodles. Garnish with green onions, sesame seeds, and cilantro.