Place sliced beef into a medium bowl and sprinkle with cornstarch. Stir to combine then set aside.

In a small bowl, add garlic, soy sauce, water, brown sugar and ginger. Stir until sugar has dissolved.

Pour sauce over meat and stir to make sure the sauce coats every piece of meat. Spray the inside of your slow cooker with cooking spray and add the beef and sauce mixture.

Cook on low for approximately 3 hours, stirring occasionally if possible. After 3 hours, add slices of yellow onion and stir to combine. Replace lid and cook on low for 1 additional hour. (If you’d rather cook the beef on high, begin checking it for tenderness after 2 hours. Once the meat is tender and sauce has thickened, add the onions.)

Just before serving, taste sauce for sweetness and add a bit more sugar if desired. Stir in sliced green onions then serve atop freshly steamed rice.