Ask your fishmonger to detach the fillets from the soles. Rinse the fillets under running water, wipe them dry then, using a sharp knife, cut them into strips 3 inches long by 1/2 inch wide. Set aside. Remove the crust, then finely grate the sandwich bread into bread crumbs. Prepare 3 plates, fill one with flour, beat the eggs, adding the oil and the water in the second one, then fill the third one with the bread crumbs. Crush the garlic in a mortar. Put the potato flesh through a sieve and add to the garlic with the egg yolk, the Cayenne pepper and the saffron. Whisk the sauce just like a mayonnaise, gradually adding the olive oil. Set aside. Dip the sole fritters first into the flour, then in the egg and last in the bread crumbs. Fry in hot oil. The cooking time is very short, the fritters should turn light brown. Drain them on a paper towel and serve with the rouille sauce on the side.
