- For prawn oil, heat 1 tbsp oil in a small saucepan over medium heat, add onion, carrot, celery and garlic and stir occasionally until tender (4-5 minutes), stir in tomato paste and stir occasionally until paste darkens (1-2 minutes). Add prawn heads and shells and stir, breaking up with the back of a wooden spoon, until coloured (3-4 minutes). Add bay leaves, peppercorns and 250ml water, bring to the simmer, then add remaining oil and simmer until well-flavoured and infused (1¼-1½ hours). Ladle oil from surface into a jug (discard liquid and solids), then strain oil through a fine sieve (discard solids). Refrigerate until chilled. Prawn oil will keep refrigerated for 3 weeks.
- Dry-roast coriander seeds until fragrant (30 seconds), then set aside. Slice prawns very thinly lengthways and arrange on a serving plate. Cut lime rind into julienne, scatter over prawns, then squeeze lime juice over. Scatter with coriander seeds, chilli and sea salt to taste, drizzle with a little prawn oil and serve immediately.
Note: The flesh for any carpaccio must be spanking fresh. Here, fresh prawns lend a sweet and clean taste. The prawn oil is great drizzled over any seafood and is particularly good tossed through seafood pasta.