Preheat oven to 160°C and line a baking tray with baking paper. Place whole cabbage on tray and roast until blackened and tender and a skewer can be inserted with little resistance (4½-5 hours). Cool briefly (5 minutes), then place another tray on top, pressing firmly to flatten cabbage slightly. Weight with heavy cans, then refrigerate to press overnight.

For pickled red cabbage, bring vinegar, sugar and a large pinch of salt to a simmer in a saucepan over medium heat. Place cabbage in a sterilised jar, then pour over pickling liquid and seal. Set aside to cool, then refrigerate (24 hours or up to 1 week).

For cabbage sauce, juice cabbage (you will need 250ml). Bring juice to a gentle simmer in a small saucepan over medium heat, then reduce heat to very low and simmer without stirring until juice clarifies and separates from pulp (15-20 minutes). Strain through a sieve lined with muslin. You should have 220ml. Add an equal quantity of stock, then bring to the boil.

Meanwhile, stir butter and flour continuously in a separate saucepan over medium heat until deep golden brown (3-4 minutes). Add hot stock mixture and stir until sauce is thick, shiny and silky (12-15 minutes). Season with salt, then pass through a fine sieve into a heatproof jug. Keep warm.

Preheat a barbecue to medium-high. Cut cabbage into wedges, then grill to char and heat through (1-2 minutes each side). Spoon XO sauce over a platter to taste. Place cabbage wedges on top. Pour over warm cabbage sauce, then garnish with pickled red cabbage, rocket, chives and breadcrumbs.