When butter is solid, its constituent parts—fat, water, and milk solids—are emulsified. Melted, the fat separates out. That's handy if you want to make clarified butter, but a pain if you want to keep melted butter emulsified. Happily, there's a nifty solution called beurre monté, made by gradually melting butter into a little hot water.
Beurre monté won't break unless heated to more than 180 degrees Fahrenheit, so you can poach in it or use it to finish partially cooked vegetables over low heat, carbonaraboy says. Unlike butter that's simply melted, you can add water-based ingredients to beurre monté and create a smooth sauce, LRunkle notes: Combine it with lemon juice and you get "a beautiful lemon butter suspension." Or mix in maple syrup and experience "pancake heaven."
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