For the beurre blanc white butter sauce, sauté the shallots in a little butter and deglaze with white wine. Pour the fish stock, reduce (3/4 of the liquid should have evaporated).
Then pour the whipped cream, reduce again and finally assemble with butter, gradually stirring cold pieces of butter into the sauce to give it a creamy, rich consistency and a nice sheen.With this white butter sauce can be made all the foam sauces and a lot of derivatives.