Toss beef with cornstarch and 1/4 tsp. salt. Heat 2 tsp. oil in skillet on high. Brown beef; add onion, garlic and red pepper; cook 30 seconds; reserve. Reduce heat, add 2 tsp. oil, kale, sugar and 1/4 tsp. salt; wilt. Add 1 cup water; simmer 5 minutes. Stir in 1/4 cup water, oyster sauce, soy sauce, water chestnuts and beef; warm through.