At the restaurant we go through a lot of seafood, so it’s easy to accumulate enough prawn and scampi shells to make an oil. At home, keep a plastic bag in the freezer and add to it when you cook shellfish. You can also use whole school prawns as a cheap, convenient alternative.
Put a heavy wide-based saucepan over a high heat. When hot, add 4 tablespoons of the oil. When the oil starts to smoke, add the prawn shells. Do not stir for at least 2 minutes (if you stir them straight away, a lot of the heat will be lost and the shells will start to stew rather than caramelise).
After 2 minutes you will start to smell that really appetising aroma of roasted prawns and you can stir the mix to further caramelise the shells. After about 5 minutes, the shells should have a nice deep red colour. Add the garlic and star anise, and stir in the tomato paste. Turn the heat down to medium.
Cook, stirring constantly, for about 5 minutes. Stir in the rest of the oil and turn the heat down to the lowest it can go. Simmer for 3 hours, remembering to scrape the bottom of the pan often, as the mixture will catch.
Strain everything through a fine sieve and leave the liquid to settle for 1 hour. All the sediment will sink to the bottom during this time. Strain the liquid a second time and carefully decant the mixture into a sterilised jar. Stop pouring when you reach the sediment. This sediment (which I call ‘shellfish essence’) can be used as a base for a shellfish sauce or dressing. You can store the shellfish oil in the fridge, covered, for up to 6 months.
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