Made this tonight, SO GOOD. Didn't have everything on hand, so I used 2 zucchini (no yellow squash), a little onion instead of shallots, and whole milk instead of cream. Zucchini and Yellow Squash Gratin - Martha Stewart Recipes
Zucchini And Tomato Bake From: Southern Bite. Made this tonight for dinner - yummy, although might pre-cook brown onion if I use it in this recipe again (recipe actually called for red onion, which probably would have been fine).