Beurre Blanc
Similar to Hollandaise it doesn't have quite the same caché, though it can be just as effective on a nice bit of fish, grilled chicken or steamed vegetables.

It's prepared by reducing wine, shallots, and herbs (typically thyme or dill), if used, until it is nearly dry. Sacrilege to some, cream can be added at this point to act as a stabilizer. Lemon juice is sometimes used in place of vinegar, and you can add stock too. Cold, one-inch cubes of butter are then gradually incorporated into the sauce as the butter melts and the mixture is whisked.
Notoriously fickle, the sauce has to be kept between 27°C, below which the butterfat separates, and 58°C, above which emulsifying proteins will break down releasing the butterfat from its suspension.

Beurre Blanc
veg sauce
A delicious sauce, though very temperature-sensitive. Too hot and it will immediately curdle. Too cold and it will separate. You can hold it in a vacuum flask for quite a while though - maybe an hour or so.

Serves 4

Place the shallots, thyme leaves, vinegar, peppercorns and wine and bring to the boil.
Lower the heat and reduce the contents for about 2 minutes until only 1 tbsp liquid remains. It should have a light syrupy consistency.
Over a gentle heat, add the water, then whisk in the butter a little at time, keeping the sauce light and foamy, until completely emulsified. Season with salt, white pepper and lemon juice as you like.
Strain into a warmed jug or vacuum flask.
The water is definitely optional, and some non-conformists will add cream - these are useful for stabilising the sauce though. The sauce is also most often served unstrained, though you'd probably want to skip the whole peppercorns then :)