From Celeste Dolan/Celestial Kitchens
[Ed: More fun with stale bread! Nuff said.]
Ingredients2 yellow onions, sliced 1 tablespoon butter 1 tablespoon olive oil kosher salt 4 tablespoons (2 ounces) unsalted butter Freshly ground black pepper 6 cups 1-inch-cubed crustless brioche 6 cups 1-inch-cubed crusty white bread 1 tablespoon finely chopped chives 1 teaspoon fresh thyme leaves 3 large eggs 3 cups whole milk 3 cups heavy cream freshly grated nutmeg 1 cup shredded gruyere
Place a medium sauté pan over medium-high heat, add butter and olive oil to pan. Add sliced onions and saute until caramelized, about 30 minutes. Adjust salt and pepper to taste.
Preheat oven to 350 degrees. While onions are cooking, spread bread cubes on a baking sheet and bake until dry and pale gold, about 20 minutes, turning pan about halfway through. Transfer to a large bowl, leaving the oven on.
Add onions, chives and thyme to the bowl of bread; toss well. In another large bowl, lightly whisk the eggs, then whisk in milk, cream, a generous pinch of salt, pepper to taste and a pinch of nutmeg.
Sprinkle 1/4 cup shredded cheese in bottom of a 9-by-13-inch baking pan. Spread 1/2 of bread mixture in pan, and sprinkle with another 1/4 cup cheese. Spread remaining bread mixture in pan, and sprinkle with another 1/4 cup cheese. Pour in enough milk mixture to cover bread, and gently press on bread so milk soaks in. Let rest 15 minutes.
Add remaining milk mixture, letting some bread cubes protrude. Sprinkle with salt and remaining cheese. Bake until set and top is brown and bubbling, about 1 1/2 hours. Internal temp should be 170 degrees. Serve hot.