Thaw the fillets of sole overnight in a colander in the refrigerator. Pat dry with absorbent paper.
In a saucepan, sauté the onion, garlic, leek and potato in olive oil. Add the water or stock and simmer for 15 minutes on a low heat. Add the spinach and cook for a further 10 minutes.
In a blender, purée the mixture with the dill, mint and lemon juice. Season to taste with salt and pepper.
In a frying pan, sauté the boiled baby potatoes with the thyme, flower of salt, and pepper. Heat a little olive oil, butter and thyme in a non-stick frying pan and sauté the fillets of sole for four minutes on each side, turning carefully with a spatula. Squeeze in the juice of one lemon and season with salt and pepper.
CHEF GEORGE ECONOMIDES