Step 1 Roast the prawns with a splash of oil in the oven until the shells start to colour and you get the wonderful aroma of roasting shellfish. Separately in a large heavy based pan sweat the onion, carrot, fennel, peppers, celery & garlic in a little oil.
Step 2 Once you have a little colour add in the wine and pastis, then all the other ingredients, fish & prawns. Bring to the boil and simmer for 1 1⁄2 hours.
Step 3 Allow to cool a little then blitz it all up with a hand blender until most of the fish, veg & prawns are blended in.
Step 4 Push it through a sieve or conical strainer, discarding the solids. Taste & season with salt & pepper, rinse out the sieve and pass again.
We make a potato based rouille by mixing half mashed potato with mayonnaise & adding a little garlic, saffron & cayenne pepper to taste.