Beurre Blanc

In a small heavy non-reactive saucepan, combine the white wine, vinegar and minced shallot. Bring to a simmer over medium heat and reduce until almost dry — only 1-2 tablespoons of syrupy, glistening liquid remain among the soft shallots, 5-7 minutes. This concentrated, acidic base is what will hold the butter in suspension.

Reduce the heat to the lowest possible flame — the reduction should be warm, never simmering. If using cream, whisk it into the reduction now and let it warm through for a minute; the cream's emulsifiers make the sauce far more forgiving. The pan should feel hot to a hovering hand but the liquid must not bubble.

Whisking constantly, add the cold butter two or three cubes at a time, letting each addition melt and emulsify into a creamy mass before adding more. Never let the butter melt to clear oil — it must soften and disappear into a thick, opaque sauce. Move the pan on and off the gentle heat as needed to keep it warm but never hot, building the emulsion cube by cube until all the butter is incorporated.

Off the heat, season the sauce with fine salt and a few drops of lemon juice, tasting as you go to balance the richness against the acidity. For a classic silken sauce, strain out the shallots through a fine sieve; for a rustic version, leave them in. Add white pepper and chives if using. Serve immediately — beurre blanc cannot be reheated or held hot for long without breaking. Keep it barely warm in a water bath if you must wait a few minutes.