Cut chicken and tomatoes into bite-sized pieces. Drain chestnuts, let drain and cut into small slices. Clean spring onions and chop coarsely. Drain the mushrooms and let them drain. Clean and rinse celery and cut crosswise into small pieces. Rinse iceberg lettuce, spin dry and chop finely.
Turn chicken in cornstarch to the other side. Cook long grain rice on stove.
Heat oil in a wok and fry the meat in it until it is no longer red inside. Add water chestnuts, tomatoes, mushrooms, onions, celery, garlic powder and soy sauce. Cover and let brew gently for 5 minutes.
Place chicken mixture on a serving platter lined with the leaf lettuce, spread and place on the table with the hot long grain rice.