Place the bones from the sea bass in a large stockpot and add the onions, bouquet garni, salt, pepper, and 6 cups water. Bring to a boil, then reduce heat to a simmer and cook for 1 hour. Strain the stock into a bowl and cool. Preheat the oven to 350F. Cook the rhubarb in boiling water for 10 minutes. Drain and purÄe in a food processor. Rub a shallow ovenproof dish with the garlic. Lay the bass fillets in the dish and season with salt and pepper. Sprinkle the shallots over the fish and pour in the white wine and 2 cups of the fish stock. Cover with aluminum foil. Bake in the oven for 20-25 minutes. Transfer the fish to a warmed serving platter and keep warm. Strain the cooking liquid into a medium saucepan and boil hard until reduced by half. Stir in the cream and boil hard until the mixture is reduced by half. Stir the purÄed rhubarb into the sauce. Pour the sauce over the fish before serving.
