Preheat your oven to 350°F (175°C).

Cut the day-old brioche into 1-inch cubes and place them in a large mixing bowl.

In another bowl, combine the eggs, half and half, vanilla, cinnamon, nutmeg, lemon juice, and salt. Whisk together until smooth.

Gently toss the peach slices with the brioche cubes, then pour the custard mixture over and fold gently.

Pour the mixture into a greased 9x13 inch baking dish, spreading evenly.

In a separate bowl, mix the flour, brown sugar, and cinnamon. Add the butter and blend until resembling coarse crumbs.

Sprinkle the crumble mixture over the custard-soaked brioche and peach mixture.

Bake for 45–60 minutes until golden brown and custard is set but slightly jiggly.

Let cool for 10 minutes before dusting with powdered sugar and serving.