Remove the leaves from the cauliflower and trim the base so it can sit upright (keep these leaves, they are delicious season with oil, salt and pepper and roasted until crispy)
Cover with a drizzle of oil and the chilli crisp (the solids of the crispy chilli oil)
Place the cauliflower in a roasting tin and wrap snugly in foil
Roast in the preheated oven for about 40 mins until starting to soften
Carefully unwrap the foil, baste with any moisture the cauliflower has released and return to the oven for another 15 mins
Melt the butter in a medium saucepan over medium heat
Stir in the flour to form a roux, cooking for 1–2 mins
Gradually pour in the milk, whisking continuously, beating out any lumps, until the sauce thickens and (around 3–4 minutes)
Remove from the heat and whisk in the parmesan, stirring until melted and smooth
Gently stir in 2-3 tbsp crispy chilli oil (a mix of the solids and oil) into the sauce to form a marbled effect
Taste and adjust salt if needed
Place the roasted cauliflower on a serving plate
Bring to the table and pour over the chilli parmesan cream, chives and sesame seeds, and crispy onions
