I do not know the answer, but OH MY~... This sounds really good. If you are looking for prepare
ahead gratin sides, I have a few....
immediately comes to mind is
Charlies broccoli / cauliflower casserole
Richards Corn Pudding Casserole
Someone posted, sorry, forget who... a wonderful spinach casserole.
If you search my name, the recipes will come up as they are my go-to....
Best,
Barb