Heat the oil in a pan.
Sauté the garlic and onion.
Add the sirloin. Continue to sauté until the beef turns medium brown.
Add the oyster sauce, soy sauce, and water. Stir. Let boil.
Cover and cook in low to medium heat for 30 to 45 minutes. You can add water if needed.
Add salt and pepper to adjust the flavor. Stir.
Put the snow peas in. Cook for 3 minutes.
Pour-in the water with cornstarch. Stir and cook until the sauce thickens.
Transfer to a serving bowl. Serve.
Share and enjoy!