In a mixing bowl, whisk together the egg yolk, vinegar and mustard. Slowly pour in the vegetable oil, whisking continuously until it is pale, thick and creamy then season with the salt. This can also be done in a mini food processor. Fold the shallots, pickled onions, cornichons, smoked eel and herbs in to make a chunky sauce and set aside.

Put the flour, eggs and breadcrumbs in separate flat containers. Remove any skin from the sole and trim the fillets to a nice finger shape. First, place the fish in the flour and coat evenly, then dip it in the egg and finally the breadcrumbs. Repeat this again so you have a thick coating on the fish. Heat the oil in a deep-fat fryer, deep saucepan or wok to 180C, or until a piece of breadcrumb sizzles straight away when dropped in. Fry the fillets for 2 mins until golden. Drain the fish on kitchen paper, season with salt and serve with a generous dollop of the smoked eel tartare sauce, lemon wedges for squeezing over and chips, peas or mushy peas, depending on preference.