Often used as a garnish or to flavor sauces and soups, duxelles is a mixture of finely chopped mushrooms, shallots and herbs cooked in butter until it forms a thick paste.
For whatever reason, I'm into words like this - French words and phrases that explain a combination of ingredients or items that serve a purpose. So pretty. See also mise en place and mirepoix. I use "my mise" all the time to justify to Cooper the piles of oils and vinegars I leave out on the countertop. Or, rather, I did. Before I had a fancy pull-out pantry shelf dedicated to salad dressing ingredients.
Also, as a minorly related aside, my sister is in Paris right now, spur of the moment. It'd be nice to be 23 and in grad school again, right?