In a large frying pan or wok, heat the oil over high heat. Cook the chicken, brown onion, and garlic for 5 minutes, breaking up lumps with a wooden spoon until the chicken browns. Stir in curry powder. Add broccoli, carrot, and mushroom; cook for 3 minutes until the vegetables start to soften.
Stir in the stock, oyster sauce, tomato sauce, and noodles. Simmer for 2 minutes. Toss in the peas and cabbage, cooking until the cabbage just begins to wilt.
Garnish the chicken chow mein with chopped spring onion and toasted sesame seeds before serving.