Prawn essence

1. Preheat the oven to 160C fan-forced or 180C conventional.

2. Spread the prawn heads on a baking tray and roast for 40 minutes - they should be cooked and quite dry. Crush the heads lightly to release any moisture, then roast for about 15 minutes more, being careful not to burn them.

3. Tip the heads into a food processor and blitz for one minute.

4. Tip the blitzed shells into a small pot with the oils and stir. Cook on a very low heat, 55-65C, and maintain in this range if you can for 45 minutes - this might be difficult on some stoves, but if you watch it and take the pan off the heat now and then to cool down, you will still get a good result. You need a thermometer for this; it shouldn't bubble or fry.

5. Once infused, strain the oil through a fine sieve lined with muslin - most of the oil will strain through quickly, but leave it to sit and drain slowly (without forcing it) to get all the essence. Cool and store in the fridge for up to a month.