How to Make It
In a skillet, heat 1 tablespoon of the vegetable oil. Add the shrimp and stir-fry over moderately high heat until curled, 2 minutes; transfer to a plate. Add 1 tablespoon of vegetable oil to the skillet. Add the chicken and stir-fry until white throughout, 3 minutes; transfer to the plate with the shrimp.
Add the remaining 1 tablespoon of oil to the skillet. Add the cabbage, onion, carrot and the mushrooms and stir-fry for 4 minutes. Add the stock, soy sauce, sesame oil, shrimp and chicken; remove from the heat.
Meanwhile, cook the udon in a pot of boiling salted water for 1 minute. Drain and add to the skillet. Stir-fry over high heat until heated through. Season with salt and pepper, garnish with scallions and serve.