Thanks to Kris Wheeler for sharing this recipe with me. As you will see - I made some changes.

Crustless Spinach and Mushroom Pie

2 large bags of spinach (I used one bag and 1 defrosted box of chopped spinach, squeezed dryish)
1 large onion thinly sliced (I used a Vidalia)
2 tbsp olive oil, plus extra for frying and drizzling
1 clove garlic, crushed. (I used more - I like garlic)
2 cups baby portabella mushrooms. (I used the contents of the supermarket container of sliced baby bellas)
6 beaten eggs
Sea Salt and freshly ground black pepper to taste (remember, your cheese will have salt in it - so don't overdo)
1 cup grated Parmesan cheese, fresh (I used half reduced fat feta and half Kraft parmesan from a jar)
Bread crumbs (I used 4C brand seasoned Panko and I like the texture it gave the final product.

Preheat the oven to 375.

Place the spinach in a large bowl and cover with boiling water, leave to wilt. Drain well and, wehn cool enough to handle, squeeze out the excess moisture

Gently soften the onion in the olive oil, until pale golden. Stir in garlic and mushrooms and add a little more oil. Cook until the mushrooms are just tender. Stir in the spinach and season to taste. allow to cool. Mix with the beaten egg and cheese. Check seasoning.

Spray a 9 x 13 pen sprayed with your favorite non-stick.. I had trouble understanding where the breadcrumbs went, so I put a very thin layer on the bottom of the pan, added the spinach mix and then topped with breadcrumbs and a sprinkling of cheese, which I drizzled with olive oil.

Instructions said to bake for 20 minutes or until the eggs set. I found that the breadcrumbs didn't brown very much and wound up baking it for 30 minutes. This is what my result looked like.

I cut it into rectangles and will freeze it to have for breakfasts (or whatever). It's quite delicious.