Wash and clean the cauliflower, separate the florets from the main stem with about 3cm stems. Cut this at the lower end and peel the lower part. Roughly grate the cauliflower except for 6 larger florets.
Bring the water to a boil, dissolve the chicken broth in it and blanch the 6 florets for 4 minutes and keep them warm. Then cook the fusilli according to the instructions on the package until al dente and strain and keep the stock.
Mix the ingredients for the sauce. Preheat the oven to 200 degrees circulating air. Wash the green part of the spring onion and cut into fine rolls.
Brush a baking dish with the butter and add half of the fusilli, cover with the cauliflower flakes and sprinkle half of the grated pecorino on top. Spread the remaining fusilli over it, drizzle with the sauce and olive oil. Sprinkle with the rest of the pecorino.
Bake the casserole on the middle rack until the cheese has melted well and has run into the fusilli. Put the casserole on a serving bowl and add the cauliflower florets. Garnish, serve warm and enjoy.