In a small bowl, whisk together all the stir fry sauce ingredients and set aside.
Heat 1 tablespoon of oil in a large frying pan or wok over medium-high heat. Add the diced onion and sauté for 2 minutes, or until it softens and turns translucent. Remove and set aside.
Add the ground beef to the pan, breaking it up as it cooks. Let it brown until crispy on the bottom for that extra depth of flavor. The pan juices will evaporate, let the beef get a nice sear before moving it around.
Stir in the minced garlic and cook for another minute, until fragrant. Add back the onions.
Pour in the stir fry sauce and stir vigorously to combine. Let it simmer until the sauce thickens and coats the beef and onions.
Serve the stir fry over freshly cooked rice, garnishing with green onions.
Optional: Crack an egg yolk on top of the hot stir fry and mix it for a creamy, velvety finish. Enjoy!