Mounting a sauce with butter

Mounting a sauce with butter

Whisk in cold butter for a smooth and glossy sauce

The technique

Off the heat or over very low heat, add the cold butter in small pieces, one at a time, whisking or swirling the pan in circular motions. Each piece must melt almost completely before adding the next, without ever letting it boil.

When to use it

To finish a wine sauce, a meat jus, or to mount a beurre blanc made from reduced shallot and vinegar. This technique transforms a thin liquid into a coating sauce just before serving.

Pitfalls

1. A base that is too hot melts the butter all at once, making the sauce oily
2. Adding all the butter at once rather than piece by piece
3. Letting the sauce boil again after adding the butter breaks the emulsion

The cue

The sauce becomes smooth, glossy, and thick enough to coat: it covers the back of a spoon without running off all at once. The ideal temperature is around 60 to 70 degrees, never simmering. If oil droplets reappear on the surface, the sauce has overheated.