Vegetarian Egg Casserole

So it's Meat Free Monday again! And again I dropped the ball on being prepared.  I was planning to make quiche, but then I found out that the puff pastry that was in the freezer needs two hours to defrost, and I didn't think that far ahead.  So, improvisation abounds! I decided to take the ingredients and make an egg casserole.

Fun fact, do you know that in Canada milk comes in bags?  Apparently this is only a Canadian thing. Oh, and I moved to Canada (which is at least part of the excuse I'm using for not updating for months).

Vegetarian Egg Casserole
Adapted from: http://www.kraftrecipes.com/recipes/quick-easy-egg-casserole-66050.aspx
1/3 of a baguette (or 3-4 slices of bread), cubed
4 eggs
1 1/3 cup milk
~1 cup grated cheese (marble cheese is delicious)*
3 handfuls cherry tomatoes, halved or quartered
1 medium onion, chopped
4 large field mushrooms, sliced
1/2 tsp cayenne
1/4 tsp nutmeg
1 tsp mustard seeds
a splash of balsamic vinegar
salt
olive oil

1. Preheat oven to 350F/175C.
2. Using cooking spray or oil, lightly grease a 9x9" casserole dish
3. Spread cubed bread in an even layer across the bottom of the casserole dish
4. Meanwhile, heat a small amount of oil in a frying pan over medium heat.
5. Add onions and fry until starting to clear, add mushrooms and soften.  
6. Throw in tomatoes and add a splash of balsamic and a pinch of salt.  Let cook 3-5 minutes on medium heat.
7. Spread sauteed vegetables on top of bread, top with cheese. 
8. Add as much cheese as you like.  The best cheese for egg casseroles or quiches is gruyere, in my opinion, but I used marble cheese instead because it's much cheaper, and I had it on hand.
9. In a medium size bowl, whisk together 4 eggs, 1 1/3 cup milk and spices.  You can use any spices you like, these are just a guideline.
10. Pour egg mixture over bread/vegetable/cheese mixture.
11. Bake for 40 minutes or until golden on top (or cooked through).
12. Let sit for a few minutes to cool, then enjoy!

Serve with your preferences of ketchup, bbq sauce or chili sauce.

Substitutions -- you could add ham, bacon or sausage meat if you crave meat.  Other vegetable choices could include spinach (cook for 30 seconds or so), cooked pumpkin/squash, garlic, broccoli, etc.