In a medium bowl, combine beef with 1 tbsp of the fish sauce, soy sauce, black pepper and sugar. Toss to mix well and let marinate for up to an hour.

Trim asparagus, breaking off bottom stalks. Cut green upper portions diagonally into 2 inch lengths. You should have about 2 cups of sliced asparagus. Set aside.

In a large skillet or wok, heat oil over high heat for 30 seconds. Add garlic and toss. Scatter beef in pan and cook briefly on one side, then toss once to sear other side. Add asparagus and toss well. Add remaining fish sauce, water and green onion. Cook tossing once or twice, until asparagus is shiny and tender, but not soft, about 1 minute. Transfer to a serving dish and serve with hot rice.