Stir-fried Onion-pepper Asparagus

• 20 trim asparagus
• 1/2 green pepper
• 270 gr asparagus
• 230 ml waterchestnuts
• 180 ml chicken broth
• 30 ml soy sauce
• 30 ml oil
• 8 gr cornstarch
• 4 slices mushrooms
• some green onions