First, boil half a cup of macaroni in salted water until just cooked. Slice 5-6 mushrooms thinly. Heat a tsp of olive oil in a pan. Add mushrooms and stir fry until they looked cooked. Add macaroni, salt and crushed pepper. Mix well, then arrange in a baking dish.
Now our second layer, the spinach sauce. Start with a small bunch of spinach. Discard any thick stems and spotted/damaged leaves, then pour boiling water to cover the spinach. Blanch for a few seconds, drain and make a fine puree. This should give you around 3/4 cup. Seperately, mix a cup of milk with a tbsp of cornflour.
Heat a tsp of olive oil. Add spinach puree and cook until it starts to look a little dry. Then add the milk/cornflour mix and cook, stirring continuously, until the sauce turns thick. Add salt and pepper to taste. Remember your macaroni's already seasoned so go a little easy here. Pour the sauce over your macaroni.
Heat the oven to 180C. Top your macaroni and spinach with breadcrumbs and bake for 10 minutes. Take it out of the oven (very carefully!) and sprinkle some grated parmesan, then put it back and bake until browned on top.