Heat the oven to 190C/fan 170C/gas 5. Butter and base-line a deep 23cm springform tin with baking paper. Wrap the bottom of the tin tightly with a couple of sheets of foil to guard against leaks.
Cook the macaroni in boiling, salted water but drain just before it’s tender as it will continue to cook in the oven. Rinse under cold water until cool then drain again.
Cook the spring onions in a knob of butter until soft then add the garlic and cook for another 2 minutes. Stir in the spring greens and a splash of water then cook for 3-4 minutes or until wilted.
Whisk together the eggs, cream and milk in a large bowl. Add 1/2 the parmesan and all of the other cheeses and mix well with lots of seasoning (especially pepper). Stir in the macaroni and the greens mixture.
Tip into the tin and smooth down, then sprinkle over the rest of the parmesan. Put on a baking tray and bake for 30-35 minutes or until set and golden. Cool in the tin for 20 minutes, loosely covered with foil, before turning out and cutting into wedges.