Beurre manié is equal parts of flour and butter kneaded together used to thicken sauces and soups.
The butter coats the flour particles and when you whisk the beurre manié into a hot or warm liquid, the butter méelts, releasing the flour particles without creating lumps.
Do not confuse beurre manié with roux which is usually cooked in butter before milk is gradually whisked in.
Here is a great video on how to make it!
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