Sauté onion and next 3 ingredients in hot oil in a large skillet or wok 1 minute. Stir in salt and pepper. Add greens; sauté 2 minutes. Add sugar and vinegar; cover and cook 3 minutes or until wilted. Remove and discard serrano pepper before serving.
*1/2 jalapeño pepper, split, may be substituted.
Try This Twist! Sautéed Greens With Pork: Stir in 1/2 lb. chopped smoked pork with greens.