Vegetable oil spray
1 loaf supermarket French or Italian bread (16 ounces), cut into 1-inch pieces (16 cups)
2½ cups whole milk
7 large eggs
1 cup heavy cream
⅓ cup granulated sugar
2 teaspoons vanilla extract
1 teaspoon ground cinnamon
¼ teaspoon ground nutmeg
½ cup packed light brown sugar
4 tablespoons (½ stick) unsalted butter, softened
2 cups candied walnuts or pecans, chopped coarse
1. Line slow cooker with aluminum foil collar, then line with foil sling and coat with vegetable oil spray. Adjust the oven rack to middle position and heat oven to 225°F. Spread bread over rimmed baking sheet and bake, shaking pan occasionally, until dry and crisp, about 40 minutes.
2. Spread bread into prepared slow cooker. Whisk milk, eggs, cream, granulated sugar, vanilla, cinnamon, and nutmeg together in bowl, then pour mixture evenly over bread. Press gently on bread to submerge.
3. Mix brown sugar and butter in medium bowl until smooth, then stir in walnuts. Sprinkle walnut mixture over casserole. Cover and cook until center of casserole is set, about 4 hours on low.
4. Let casserole cool for 20 minutes. To serve, either spoon casserole onto individual plates or transfer casserole to serving platter using sling.