Start by making your hoisin sauce. Put all of the hoisin sauce ingredients into a jug and blend with a stick blender until thick and smooth.
Heat the sesame oil in a wok over a high heat. Slice the bell peppers and mushrooms and add to the wok. Stir fry for 2 minutes, then add the duck. Stir fry for another minutes.
Add the noodles and hoisin sauce. Continue to stir fry until the noodles have loosened and everything is coated in the hoisin sauce. Serve immediately.