In a bowl, combine 3 tablespoons cornstarch, 3 tablespoons water, minced garlic and salt until smooth. Add the sliced beef and toss.
In a large skillet over medium high heat, stir-fry beef in 1 tablespoon oil until beef reaches desired doneness; remove and keep warm.
Stir-fry broccoli and onion in remaining oil for 4-5 minutes, or until broccoli is tender.
Return beef to pan.
Combine soy sauce, brown sugar, ginger, remaining cornstarch and water until smooth; add to the pan.
Stir fry for 2 minutes. Add chopped avocado. Cook for an additional 1 minute.
Remove from skillet and serve over fried rice (I like this recipe.)