A quick technique to add thickness and sheen to your sauces is to use kneaded butter, or "buerre manie".
This is a last-minute thickener, added to a sauce or a stew that is not quite as thick as you would like, just before serving.
To knead butter, simply mix together an equal portion of butter and flour, using your fingers or a fork, until the mixture forms a thick paste that is then rolled into pea sized balls. Whisk a few in at a time and whisk until completely incorporated. Repeat until you reach the desired consistency.
