In a deep saucepan combine butter and cream. Place over high heat until butter is melted and mixture starts to simmer.
Lower the heat and let the cream and butter cook slowly, stirring only occasionally, being sure to scrape the bottom of the pot thoroughly each time.
When the mixture begins to separate, raise the heat to medium and begin to whisk the mixture every couple of minutes. The goal is to allow the fat to rise to the top and the milk solids to fall to the bottom of the pot, where they will brown. Whisk the mixture to make sure that the milk solids brown evenly but not hard enough to re-emulsify them with the fat.
When the liquid turns dark caramel in color and the aroma is fragrant and nutty, remove the pan from the heat. Very slowly add half of the vinegar while whisking. If you pour too fast, the hot butter will boil over.
Pour the butter into a heat-proof bowl or jar and let cool. Once cooled, skim the clarified butter from the top. This flavorful brown butter can be stored in a jar and kept in a cupboard, ready to use for any general cooking.
Using a hand blender, slowly emulsify the remaining vinegar into the remaining browned parts of the butter just until it becomes smooth and glossy. Season with salt. You are looking for a nice tang from the vinegar to balance the richness of the browned butter, and just enough salt to make the flavor shine.