Difficulty:[usr 2]
Prepare the galette:peel the potatoes and set aside 250g; grate them finely in a food processor, fine grid. Drain them for 15 minutes in a colander then squeeze them:only 200 g remain; put them in a terrine.
Peel the onions and set aside 100g; finely chop them. Put half of the oil and 20 g of butter in a 24 cm non-stick frying pan. Add the sugar, salt and pepper. Pour 2 tablespoons of water and bring to a boil. Add the onions and cook for 5 minutes, until the onions are caramelized. Put them in the salad bowl containing the potatoes. Add salt, pepper, nutmeg and mix.
Put 20 g of butter and oil in the pan and add the contents of the salad bowl. Flatten the pancake with a flexible spatula and cook for 7 minutes over low heat. Flip the pancake and cook for another 7 minutes. Keep the galette warm and cut it in half when serving.
Prepare the soles. Ask your fishmonger to remove the brown skin from the soles and scrape off the white skin and gut them. Rinse them and pat them dry. Dip them in the flour and shake them to remove the excess:they are just veiled. Melt 25 g of butter in a 26 cm non-stick frying pan. Put them in the pan, head to tail, thick side down. Let them cook for 10 minutes over low heat until the soles are golden brown. While cooking, gently lift the fish and slide them with the small slivers of butter. When the soles are golden, turn them over with a spatula and cook until the second side is golden; slide a few slivers of butter as before under the sole. You need a total of about 100 g of butter which should never darken, but remain blond.
Arrange the soles on 2 warm plates, coat them with butter and serve with the potato pancake.
