Provençal bourride (fish stew with aïoli)

Method

1. Put all the stock ingredients in a large pan with 2.5 litres water. Bring to a simmer and cook for 1 hour, skimming off any scum floating on the top every now and then, until fragrant. Strain the stock (discard bones and veg), then set aside. You should have 1-1.2 litres fish stock.
2. Meanwhile, make the aïoli. Whizz the garlic with the 3 egg yolks, the vinegar and a large pinch of salt in a food processor for 2-3 minutes until very smooth and paler in colour. With the motor running, gradually pour in the 250ml olive oil in a very thin stream. The mixture will thicken and emulsify into a rich mayonnaise. Next, whizz in the extra-virgin olive oil, then taste and season with lemon juice, if needed, and plenty more salt. Set aside.
3. To make the fish stew, heat the 2 tbsp oil in a large saucepan or sauté pan with a lid. Add the onion and leek with some salt and cook over a medium heat, stirring often, for 10 minutes until softened but not coloured. Turn up the heat, pour in the 200ml white wine and bubble to reduce by two thirds. Pour in the reserved fish stock, bring to a simmer, then add the potatoes and cook, covered, for 15 minutes until just tender. Turn the heat down, carefully add the fish fillets, then cook gently, uncovered, for 3-4 minutes until just opaque and flaking – don’t move them while they’re cooking or they’ll break up.
4. Divide the toasted baguette slices among 6 shallow soup bowls, then use a slotted spoon to remove the fish and potatoes from the broth and divide among the bowls.
5. Put half the aïoli in a medium bowl, then whisk in the remaining egg yolk, followed by a cup of the hot broth. Once smooth, whisk this back into the pan of broth, off the heat. Return the pan to a very low heat and cook, stirring, without boiling, for 3-5 minutes until slightly thickened. Taste and adjust the seasoning, stir in the parsley and the extra splash of wine, then ladle the hot broth over the fish in the bowls. Serve immediately, with the extra baguette and the remaining aïoli.