Grilled Cheese Casserole

I promise I will do posts on topics besides food, but this recipe is from a book I need to return to the library.

Adapted from Reeve Lindbergh's Forward From Here an excellent book that is not a cookbook but contains a recipe she calls Aunt Ellie's Cheese Puff. We've dubbed it:

Grilled Cheese Casserole
5 eggs
2 1/2 cups milk
8 slices sourdough - buttered and diced (these are hefty slices)
8 oz sharp cheddar - grated
salt, pepper and dry mustard

Preheat oven to 400/375 convect. Butter a 9 x 13 baking dish. Place half the diced bread in the dish, cover with cheese, sprinkle with mustard, a liberal amount of pepper and a bit of salt. Repeat. Beat the eggs and add the milk to them. (I used my quart-sized Pyrex measuring cup for this which made the next step easy). Pour evenly over the baking dish. Put in oven and bake 45 minutes (conventional oven will take longer) or until nicely puffed and browned.