Beurre Blanc, white butter, is a hot butter sauce that is truly amazing sauce, it is light tangy and will amaze anyone who tastes it, but what is it? It's butter. Designed for fish, but I think I'd take it on practically anything.
For four portions
Having fried your piece of fish in a good saute pan and keeping the fish warm, throw into the pan 2.5 fl oz of white wine vinegar and the same of white wine and half a shallot finely diced. Using the liquid to deglaze the pan, boil until reduced to about half. Using about 350g of chilled butter cut into small chunks, start throwing chunks of butter in the pan whisking as it melts, lower the heat and keep adding the butter until it has all creamed in. This is the magic, the acid keeps the butter in emulsion, so as it melts it doesn't separate, but turns into this light ivory coloured, wonderful, warm tangy, light, Hollandaise style sauce.
For other good reasons to use butter follow this link: http://authoritynutrition.com/7-reasons-why-butter-is-good-for-you/