This zucchini gratin is a flavorful side dish casserole with extra richness from the cheddar cheese. A gratin is a baked dish with a creamy sauce and crunchy topping, and is always a nice way to make a fancy side dish out of everyday vegetables. If you or your neighbors have an abundance of garden-fresh summer squash or zucchini, this is an excellent way to use it. The casserole is a good choice for a holiday meal or sunday dinner, and it is a nice low-carb replacement for scalloped potatoes or mashed potatoes.