Dutch-Oven Fish with Mushrooms

Soak 100 g of dried mushrooms in water, then boil them and drain them in a colander.
Cut 1 kilogram of fish into pieces, remove the bones, and sauté the pieces until golden brown.
In a saucepan, cook 500 g of onions in 1 cup of oil, then add 1 tablespoon of flour, plus pepper and salt, and remove the pan from the heat.
In a Dutch oven, layer the fish, onions, and mushrooms, then place the Dutch oven in a moderate oven for one and a half hours.