Everyone loves to wake up to French toast, but it can be time consuming to cook for a crowd. That's the beauty of this recipe: the French toast is baked rather than sautéed, making serving so much simpler! Feel free to substitute or combine other berries as you like.
Position a rack in the lower third of the oven and preheat to 350 degrees F. Butter a 9x13-inch baking dish and one side of a sheet of aluminum foil that's large enough to cover the baking dish; set aside.
Place the eggs in a large bowl and whisk to blend. Add the milk, half and half, vanilla, sugar, nutmeg and cinnamon, and whisk to combine.
In a separate bowl, toss the blueberries with the cornstarch.
Pour about one third of the egg batter into the prepared baking dish. Add one third of the blueberries to the dish. Cover the bottom of the dish with half of the bread slices, cutting them to fit in a single layer.
Pour half of the remaining batter over the bread, then sprinkle with half of the remaining blueberries. Cover with the remaining bread and repeat with the remaining batter and berries. Push the bread into the batter with your fingers so that it gets moistened.
Cover the baking dish with the sheet of aluminum foil, buttered side down. Bake for 20 minutes, then remove the foil and bake until the dish is set and lightly golden, 20 to 30 minutes more. Serve warm with maple syrup and additional fresh blueberries on the side, if desired.