Heat one tablespoon oil in a large frying pan over medium-high heat. Cook mushrooms for 3-4 minutes or until browned. Add garlic, peppercorns and Chinese five spice and cook for a further minute or until fragrant. Stir through soy sauce, tahini, honey, stock, tofu and choy sum. Simmer for 1-2 minutes or until choy sum is tender and sauce has slightly reduced. Stir through sesame oil.
Bring a large saucepan of water to the boil. Boil egg noodles for 3-4 minutes or until tender. Drain and set aside.
Divide noodles between four serving bowls. Top with mushroom mixture and the sauce, then finish with spring onion and coriander leaves.