THE DAY BEFORE SERVING THE STRATA:

• Heat a large, heavy skillet over medium high heat. When the skillet is hot, add ½ pound bacon and cook until crispy. Transfer the bacon to a dish lined with paper towels to soak up excess grease. Discard all but one tablespoon of the bacon grease.
• Add 16 ounces baby bella or button mushrooms to the skillet and a pinch of salt. Cook, stirring occasionally until the mushrooms give up their liquid and begin to brown.
• In a large bowl, combine 5 cups stale Italian or Sourdough bread, crisped bacon, browned mushrooms and 1 cup caramelized onions. The caramelized onions may stick together, so use your fingers to spread them apart and toss the mixture until everything is evenly combined.
• Add ¼ cup chopped parsley and 2 cups shredded mozzarella cheese, then toss again to distribute the ingredients evenly.
• Spray a 2 quart casserole with vegetable spray. Transfer the bread mixture to the casserole and spread evenly.
• In a small bowl, whisk together 5 large eggs, 1 ¼ cups milk, ½ teaspoon kosher salt, ¼ teaspoon white pepper, ⅛ teaspoon cayenne pepper, ¼ teaspoon dry mustard, ½ teaspoon dried thyme and ½ teaspoon onion powder. Pour the egg mixture evenly over the strata. Cover with plastic wrap and refrigerate for several hours or overnight.
• Remove the casserole from the refrigerator about half an hour before baking to take the chill off.
• Preheat the oven to 375°. When the oven has heated, place the casserole in the center of the oven and bake for 50-60 minutes, or until the center has cooked through and the top is golden and puffed.
• Remove from the oven and let rest for 10 minutes before serving.