Preheat oven to 220°C fan-forced. Toss the cauliflower florets with 3 tbsp of the olive oil and a generous pinch of salt. Spread in a single layer on a baking tray. Add the cauliflower leaves separately.

Roast for 25 minutes, turning halfway, until deeply browned at the edges. Reserve a third of the florets and the roasted leaves for garnish.

Heat the butter and remaining 1 tbsp olive oil in a large heavy pot over medium-low heat. Sweat the onion 8 minutes until soft. Add the garlic, cook 1 minute.

Add the remaining roasted cauliflower and the stock. Bring to a simmer; cook 10 minutes.

Take the pot off the heat. Blend with a stick blender until silky smooth (or transfer to a high-speed blender in batches).

Return to low heat. Stir in the cream and the parmesan off the heat (or with the heat very low). Add the nutmeg, season generously.

Ladle into warm bowls. Top each with a scatter of the reserved roasted florets, a few roasted leaves, a swirl of best-quality olive oil, an extra grating of parmesan, and a few cracks of black pepper. Croutons on the side if you like.