Steps

1. Heat a sauté pan over medium-high flame. Add 2 tablespoons of the butter and the mushrooms and sauté until the mushrooms are browned. Remove and cool to room temperature.
2. In a large bowl, beat together the eggs, milk and salt. Butter a 9x9-inch baking dish with the remaining tablespoon of butter. Arrange 4 slices of bread in the baking dish in one layer. Spread the ham and 1/2 cup of the cheese in an even layer over the bread slices. Pour about 1 cup of the milk-egg mixture over top.
3. Arrange 4 more bread slices in the dish and press gently into the bottom layer. Spread the spinach evenly over the bread slices and season with pepper. Top with 1/2 cup cheese and pour about 1 cup of the milk-egg mixture over it.
4. Add 4 more bread slices and press to firm the layers. Spread the mushrooms and 1/2 cup of cheese over this layer and pour over another 1 cup of the milk-egg mixture.
5. Lay the remaining 4 bread slices on the top of the strata and press down gently to firm the layers underneath. Pour the remaining custard over the top, cover the baking dish with plastic wrap and refrigerate it for at least 2 hours or overnight. Reserve the remaining 1/2 cup of cheese.
6. Preheat oven to 325°F. Remove the baking dish from the refrigerator, uncover, and place it on a baking sheet lined with aluminum foil. Allow the strata to stand at room temperature for 1/2 hour, and then bake for about 1 hour until it is puffed and light golden brown and a knife blade inserted into the center comes out clean.
7. Turn on the broiler. Sprinkle the remaining cheese over the top of the strata and place it under the broiler until the cheese melts and begins to brown. Serve immediately.

Notes

Strata has become one of North America’s most popular brunch entrées. It is a completely make-ahead dish. If you assemble the strata in the evening, all you need to do the next morning is pop it in the oven. You’ll have a tasty and impressive main course for breakfast or brunch.

Strata means "layers," and that’s what your guests will discover when they dig into this savory bread pudding–layers of tasty ham, spinach, and mushrooms bound with a rich, cheesy, quiche-like custard.

You can vary the ingredients in the layers to suit your taste. Make an Italian strata with sausage, tomato sauce, and provolone cheese, or create a vegetarian strata with well seasoned cooked vegetables of your choice.