Melt sugar in a heavy-based pan until it forms a golden-brown caramel.
Remove pan from heat and stir in sultanas, rosemary, ginger, shallot, and rhubarb.
Add cider vinegar and orange juice then boil gently for 8 to 10 minutes.
Season chutney with salt and pepper and set aside to cool.
Combine orange segments, chicory, pea shoots, celery tops, and dill in a bowl.
Dress the salad with rapeseed oil and season with salt and pepper.
Place mackerel fillets skin-side up on an oven tray and brush with oil.
Use a blow torch or hot grill to cook both sides of the fish evenly.
Serve fish with a spoonful of chutney and the prepared salad.
Garnish the final plate with ribbons of raw rhubarb.