This vegetarian version of Croque Monsieur starts with thick, crusty slices of white sandwich bread. I stuff the inside with chargrilled slices of zucchini made earthy with herbes de Provence and tons of Emmenthaler, which gives a more delicate flavor than traditional Gruyère. Over the top goes a béchamel flavored with piquant Dijon mustard and a scrape of nutmeg. Then, more cheese, set under the broiler to bubble and blister. It's everything you want in a Croque Monsieur, made just slightly more delicate—hence, Croque Mademoiselle.
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