According to Wikipedia: Gratin is a culinary technique in which an ingredient is topped with a browned crust, often using breadcrumbs, grated cheese, egg or butter. The term may be applied to any dish made using this method. Gratin is usually prepared in a shallow dish of some kind. A gratin is baked or cooked under an overhead grill or broiler to form a golden crust on top and is often served in its baking dish.

A gratin dish is a shallow oven-proof container used to prepare gratins and similar dishes.

I love to gratinee all sorts of vegetables and potatoes, either layering them with a smooth Bechamel sauce, or mixing them into the sauce and then smothering the casserole with cheese.  Spinach, broccoli, cauliflower, brussel sprouts… they make a delicious side dish to grilled meats and roasts.  When I made this dish, I was in the mood for something simple, not spicy, but satisfying.  I wanted a one dish meal that I could put together and set aside until I was ready to slide it into the oven and sit down with a glass of wine.  I had some leftover roasted potatoes in the frig, and a bag of green peas in the freezer.  And who doesn’t love ground beef fried up with onions?  This is the ultimate comfort food casserole.  The bubbly cheesy topping was deliciously indulgent and the Bechamel was light and creamy.  There are all sorts of ways you could add spice to this dish.  In fact, you could boil some pasta and spice up the beef mixture with cinnamon and you would have a Greek dish called Pastitsio.  That wasn’t what I was in the mood for when I created this casserole, but next weekend might be the perfect time for a Greek salad and a meaty casserole.