Prepare the barbecue for indirect cooking over medium heat (190°C to 230°C). If using a Weber® Q™ barbecue, set up your barbecue with a convection tray and a trivet.
Wash the cauliflower. Remove any unwanted leaves and if needed, cut the base of the stalk to create a flat surface.
In a bowl, mix together the butter, crushed garlic, salt, pepper, parmesan, rosemary and thyme. Spread the butter mixture over the cauliflower. Sprinkle the dukkah evenly over the cauliflower.
Roast the cauliflower over indirect medium heat for 1 to 1.5 hours. If the cauliflower has started to darken, cover with aluminium foil until cooked through to your liking.