The croque monsieur -- literally "mister crunch" -- is at the elegant end of the grilled cheese spectrum. First served in 1910 at a Paris cafe, this ham sandwich with rich bechamel sauce is topped with cheese and then grilled under the broiler.
When it comes to radiating warmth at the dinner table, nothing beats a meal-in-one casserole. What's more, this dish can be assembled a day ahead, goes straight from the oven to the table, and offers help-yourself allure in abundance.
The dish can be largely assembled ahead: Leave off the last portion of cheese, cover the dish with plastic wrap (pressing it directly onto the surface to prevent a skin from forming), and refrigerate it for up to one day. Remove it 30 minutes before baking, sprinkle with the remaining cheese, and bake as instructed.
You can roast the squash and prepare the bechamel and filling (omitting the egg) up to two days before assembling the lasagna; let each cool before refrigerating in separate containers. Stir the egg into the filling just before using.