6cups1-inch bread cubes with crustsa hearty French bread works well
½tspground black pepper
Butter for dish
Heat 1 tbsp oil in a large nonstick skillet over medium-high heat and add onions; stir to coat. Cook until onions start to soften, about 2 min, then reduce heat to medium and cook until onions are golden and soft, stirring occasionally, about 20 min; remove from skillet and wipe clean. Heat 1 tbsp oil in skillet, add mushrooms and sauté until golden, 3 to 4 min.
In a large bowl combine onions, mushrooms, bacon, thyme, cheese and bread cubes. Mix together the eggs, milk, salt and pepper and pour over bread, stirring to coat.
Butter a 2½- to 3-qt baking dish and arrange bread mixture evenly in dish. Cover with plastic wrap and chill 4 hr or up to 24 hr.
Heat oven to 350°F. Remove plastic wrap and bake strata until eggs are set and top is golden brown, about 50 min; cover with foil if top gets too brown. Serve warm or at room temperature.
• I love to cook this as a make ahead Christmas breakfast. Thanksgiving and New Year's are perfect times to serve this as well.