Rouille (which means rather prosaically ‘rust’) is a word impossible to properly pronounce if you are not French!
Rouille is the reddish, garlicky-spicy mayonnaise that is usually served with the most royal of fish stews; bouillabaisse. Rouille is a fantastic accompaniment to most seafood and especially shellfish, though crab is the one exception for its flavour is too delicate and the rouille overpowers it.
A quick search on google will show you that there are probably as many differing recipes for rouille as there are days in the year but here is mine:
3 egg yolks
½ tsp Dijon mustard
2 cloves garlic, blanched in their skin for 2 minutess, then peeled and mashed
1 tbsp fish broth with a good pinch of saffron strands infused
Splash of Worcester sauce
¼ tsp picante pimentón (or more if brave)
300ml extra virgin olive oil
1 tbsp fresh lemon juice
Combine all the ingredients except the olive oil and lemon juice in a food processor and turn it on.
Slowly add olive oil in a thin stream until a thick, mayonnaise like consistency is achieved. You will need approximately 300ml olive oil, but maybe a little bit more. Then add fresh squeezed lemon juice to taste (approx 1 tbsp).
This will keep in the fridge in a sealed container for quite a while, certainly for 3 or 4 days.