-
1
Grease a 9-by-13-inch (3-quart) casserole dish with oil.
-
2
Toss the bread cubes with 2 tablespoons of the oil, 1/4 teaspoon salt and a few grinds of pepper in a large bowl.
-
3
Heat a large skillet over medium heat.
-
4
Add the bread to the skillet, and cook, tossing occasionally, until toasted and golden brown, about 8 minutes.
-
5
Return the toasted bread to the bowl to cool.
-
6
Wipe out the skillet.
-
7
Heat the remaining 2 tablespoons oil over medium-high heat until it starts to shimmer.
-
8
Add the mushrooms in one layer (resist the urge to stir right away), and cook until they start to brown, about 3 minutes; stir, then continue to brown for 2 minutes more.
-
9
Add the garlic, thyme, 1/4 teaspoon salt and some pepper, stir continuously for 1 minute, then fold in the spinach and another 1/4 teaspoon salt.
-
10
Continue to cook, stirring often, until the spinach is wilted, 1 to 2 minutes.
-
11
Remove from the heat.s
-
12
Place half the bread cubes in the prepared casserole dish, and sprinkle them with half each of the Gruyere and Parmesan.
-
13
Add the mushroom-spinach mixture in an even layer.
-
14
Top with the remaining bread cubes, Gruyere and Parmesan.
-
15
In a large bowl, whisk together the eggs, half-and-half, 1/2 teaspoon salt and several grinds of pepper.
-
16
Pour the egg mixture into the casserole dish.
-
17
Cover with plastic wrap, and refrigerate for at least 6 hours up to overnight.
-
18
Remove the casserole from the refrigerator 30 minutes before baking.
-
19
Preheat the oven to 350 degrees F. Bake the casserole until the custard is set and the top is golden brown, 50 to 55 minutes.
-
20
Cool for at least 15 minutes before serving warm or at room temperature.
