Before you start, bring a large pot of salted water to the boil with the lid on.
Prep mushrooms, bok choy and spring onion and set aside separately.
Heat oil in a large, non-stick fry-pan on medium-high heat. Cook mushrooms with a pinch of salt for 3-4 minutes, until softened and browned. Remove mushrooms from pan, set aside and reserve pan.
Heat oil in reserved reserved pan on medium-high heat. Cook 'mince' for about 5 minutes, breaking it up with a wooden spoon, until browned and almost cooked through. Add Asian garlic five spice, cooked mushrooms and hoisin sauce (recipe below) and cook for a further 1-2 minutes, until sticky and cooked through. Keep warm.
Add noodles and bok choy to pot of boiling water, stir, cover and turn off heat. Leave for about 6 minutes, until tender. Add baby spinach to pot, drain and rinse with warm water. Drain again, then return to pot with sesame oil.
Serve noodles and 'mince' topped with spring onion, peanuts, remaining hoisin sauce and chilli oil (if desired).