Start by greasing a 9x13-inch baking dish. Spread the bread cubes evenly inside. Brioche or challah works best here because these breads soak up the custard without falling apart.

In a large bowl, whisk together the eggs, milk, cream, both sugars, cinnamon, vanilla extract, and salt. Mix until everything is smooth and fully combined. This mixture will coat the bread and give it that classic French toast flavor.

Pour the custard mixture evenly over the bread cubes. Use a spoon or spatula to gently press the bread so it absorbs the custard. It’s important to make sure every piece of bread gets soaked so the flavors are evenly spread.

Cover the baking dish with plastic wrap and refrigerate it for at least 2 hours, or preferably overnight. This soaking step is key, it lets the bread absorb all the custard, making it soft and flavorful when baked.

When you’re ready to bake, preheat the oven to 350°F (175°C). In a small bowl, combine the brown sugar and cinnamon. Add the cold butter cubes and use a fork or your fingers to mix it until the mixture is crumbly. If you like a little crunch, feel free to add chopped pecans or walnuts.

Sprinkle the topping over the soaked bread. Make sure the bread is evenly covered. Then, bake in the preheated oven for 45–55 minutes, or until the top is golden brown and crispy, and the center is set. Keep an eye on it to avoid over-baking, as you want the top to be perfectly crisp without getting too dark.

Let the French toast cool for about 5–10 minutes before serving. This will help it set and make it easier to slice. Serve it with maple syrup, a dusting of powdered sugar, or fresh berries for an added touch.