Beurre Blanc: A Classic Butter Sauce

Beurre blanc is a classic French butter sauce built on a reduction of white wine, vinegar and shallots, into which cold butter is whisked gradually to create a smooth, emulsified sauce. In this episode, Ash makes a variation using buttermilk, with lime, yuzu and green bird's eye chili adding brightness and heat. The key to a successful beurre blanc is temperature control: if the pan gets too hot, the emulsion breaks and the butter separates. At home, keep the heat very gentle and add cold butter in small cubes, whisking constantly. The finished sauce should be silky, glossy and just thick enough to coat the back of a spoon lightly.