1. Combine water, fish sauce, lime juice, sugar, lemon grass, and pepper flakes in bowl.

2. Heat oil in 12-inch nonstick skillet over high heat until smoking. Add asparagus and onion and cook, stirring occasionally, until asparagus is spotty brown, 3 to 4 minutes. Add fish sauce mixture and cook, stirring once or twice, until pan is almost dry and asparagus is crisp-tender, 1 to 2 minutes. Transfer to serving platter, sprinkle with mint, and serve.

Serves 4