You need good fish stock for this to work well. Your own home-made would be best, otherwise combine two 500ml pots of fresh bought stuff and reduce it by simmering to 600ml.
Prep time: 20 minutes, plus 3-4 hours marinating | Cooking time: 40 minutes
For the red mullet
8 red mullet fillets juice
10 black peppercorns, crushed
4 tbsp extra-virgin olive oil, plus extra for frying
For the aioli
2 egg yolks
2 cloves garlic, crushed smidgen
150ml olive oil
150ml sunflower oil
Lemon juice, to taste
White wine vinegar, to taste
For the broth
2 slim leeks
3 small fennel bulbs
8 waxy baby potatoes, peeled and halved
6 shallots, sliced
2 tbsp olive oil
Small dried chilli, crumbled (optional)
Generous pinch saffron
600ml well-flavoured fish stock
In a dish, coat the red mullet in the orange juice, pepper and oil. Cover with clingfilm and refrigerate for three to four hours.
For the aioli, put the egg yolks in a bowl with the garlic, mustard and a little salt. Add the oil drop by drop, stirring with a wooden spoon or beating with a hand mixer as you do so. Only add more oil when the previous lot has been well incorporated and the mixture has thickened. After all the oil has been added, add the lemon juice and wine vinegar and season. Cover and refrigerate until needed.
Trim the base and top off the leeks and remove any tough or discoloured leaves. Cut into 3cm lengths. Wash out any grit without breaking up the pieces of leek.
Trim the fennel tips, reserving any feathery bits, and removing any tough outer leaves. Quarter the bulbs lengthways and carefully trim the base of each, keeping the quarters intact. Cook the potatoes in boiling salted water for about 12 to 15 minutes, until tender.
Gently sauté the shallots, leeks and fennel in the oil for about five minutes, until slightly soft. Add the chilli, saffron and stock and bring to the boil. Immediately turn down to a simmer and cook, uncovered, for about 15 minutes, adding the potatoes a few minutes before the end. The liquid should reduce a little, leaving enough to fill four soup plates. Add the reserved fronds at the end of the cooking time.
Take the mullet fillets out of their marinade and heat two thick-bottomed frying-pans. Heat a scant ½ tbsp of olive oil in each pan and cook the mullet for about a minute on each side, turning them carefully, over a medium heat for the skin side and low on the flesh side.
Ladle the hot broth and vegetables into shallow soup plates and place two fillets, skin-side up, on top of each serving. Serve with a dollop of aioli.