In a medium sized pan, bring roughly 6 cups (1.5 liters) water to a boil and add salt. Boil the cauliflower florets for 8 minutes until just done, then briefly drain.

Step 2

Meanwhile, heat 4 teaspoons butter in a skillet. Saute the onion for 1 or so minutes, until just translucent, then add the spinach and let it wilt before setting the pan aside.

Step 3

Preheat oven to 400-degrees F (200-degrees C).

Step 4

Blitz the cauliflower in a food processor with the heavy cream and remaining butter, until crumbly. Add it to the skillet, mixing it with the spinach and the next 4 ingredients (mozzarella - nutmeg). Season with salt and pepper.

Step 5

Place it in a 8-inch (20-centimeter) square baking dish; place it in the oven and bake in the center of the oven for 20 minutes, until the cheese is golden brown. Remove from the dish and serve on plates.