In Asia they often finish off noodle or rice dishes with eggs, be they cooked in a wok or, as here, in a broth.This is a great dish for practicing your egg poaching skills as it doesn’t matter if they break into strands.
Pour 3 cups water into a saucepan and bring to a simmer over medium heat. Add the miso paste, ginger, sliced shiitake mushrooms, and a dash of soy sauce and simmer gently for 5 minutes to flavor.
Finely slice the portobello mushrooms. Divide them equally, along with the noodles and spinach, between 2 warm serving bowls. Pour over a ladleful of stock to wilt the spinach, and keep warm.
Break the eggs into individual ramekins or mugs and drop one at a time into the gently simmering stock. Poach for 2–3 minutes (it doesn’t matter if they break up slightly).
Spoon the eggs into the serving bowls with a slotted spoon and pour the stock around them, dividing the shiitake mushrooms equally between the bowls.
Serve garnished with scallions and with extra soy sauce on the side to flavor as needed.