Preheat oven to 180C fan forced or 200C convection.
Cook macaroni in a large pot of salted water according to packet instructions.
Sauté mushrooms in a medium saucepan with a splash of oil and a tbsp of butter till golden. Season and set aside (but don’t clean the pan).
Start the cheese sauce by melting the butter in the same pan and add the flour.
Cook, stirring for 1 minute over medium-low heat.
Gradually add the milk, whisking until smooth. Stir gently until mixture comes just to the boil, then reduce heat and simmer for 2 minutes.
Remove from the heat and add grated cheese and stir until melted and smooth.
Meanwhile, in a separate pan, wilt spinach with some olive oil and seasoning for 10-20 seconds. Drain excess water.
Drain pasta and return to the pan. Pour the cheese sauce over the pasta, add mushrooms and spinach and stir until coated.
Season, sprinkle with chives and pour into a lightly greased standard muffin tray. Bake for 10 minutes.
Serve warm or cool.