Step 1

Preheat oven to 400° F

Step 2

Place the bread cubes on a baking sheet and toast in the oven until golden brown, about 10 minutes

Step 3

Remove from the oven and set aside.In a large sauté pan over medium heat, cook the onions, mushrooms and herbs in the butter until vegetables are softened, about 7 minutes

Step 4

Add the spinach to the pan and cook another 5 minutes until the spinach is wilted and completely cooked down

Step 5

Pull the pan off the heat, and let cool

Step 6

In a 9 inch square or round casserole (or a 9 inch springform pan) measure out the toasted bread

Step 7

The amount of bread you need should fill the dish

Step 8

Once you have measured this, place that amount of bread back into the empty mixing bowl

Step 9

Add the onion mushroom mixture and 2 cups of swiss cheese to the bread in the mixing bowl

Step 10

Toss to combine.Turn oven down to 350° F

Step 11

In a blender combine the eggs, milk, cream, salt, pepper, mustard and nutmeg

Step 12

Blend for 10 seconds until combined.Line your dish with parchment paper or lightly grease the dish

Step 13

Add the bread and mushroom onion mixture to the pan

Step 14

Carefully pour the egg mixture over the bread

Step 15

Press the bread cubes down to make sure they are totally submerged

Step 16

Note: This step can be made the night before

Step 17

Bake the strata uncovered until it has has puffed slightly, is golden brown on top and does not shimmy with uncooked egg mixture when you shake the pan, about 1 hour and 15 minutes

Step 18

If the strata gets too dark, cover with foil and continue cooking

Step 19

Let the strata cool in the pan on a wire rack for 15 minutes

Step 20

Serve strata warm or at room temp.