Combine the wine, vinegar, and shallot in a heavy saucepan over moderate heat and bring to a vigorous boil. Let it bubble away until it's thick and syrupy — you should have about 2-3 tablespoons left, which takes roughly 5-6 minutes. Stir in the cream, salt, and pepper, then boil for exactly 1 minute. Lower the heat to moderately low and begin the butter dance: add a few tablespoons of the cold butter while whisking constantly. Keep adding the remaining pieces one by one, whisking furiously and adding each new piece before the previous one completely disappears. If the sauce gets too hot and starts to break, lift the pan off the heat for a few seconds to cool it down.
⏱ 5 min