It is a delicious casserole dish, also called as strata (or stratta), and very similar to this Brazilian Blender Pie, quiche or frittata, made from a mixture which mainly consists of bread, eggs, milk and cheese. It may also include meat and/or vegetables.
I hate to waste anything, and this is a very simple solution for the leftover bread. You can eat it for brunch, lunch or dinner.
This elegant casserole dish of cubes of bread baked in custard is often a lifesaver on busy days and within 10 minutes you can have it in the oven! You can also assemble it the night before and pop it in the oven as soon as you wake up. I also like it because you can pretty much use whatever you want as a filling. For this one I used cheese and smoked ham but the recipe is pretty flexible so you can play around with different meat and/or sautéed vegetables depending on what you have on hand.