Cut the brioche or challah bread into thick slices, about 1-inch each. Arrange the slices in the 9x13 inch baking dish, standing them upright.

In a large mixing bowl, whisk together the eggs, whole milk, heavy cream, granulated sugar, vanilla extract, ground cinnamon, and salt until thoroughly combined.

Pour the egg mixture evenly over the bread slices, pressing down gently on the slices to ensure each piece is well-coated and submerged.

Cover the baking dish tightly with plastic wrap and refrigerate overnight, or for at least 4 hours.

Preheat your oven to 350°F (175°C).

Remove the plastic wrap from the baking dish and bake the French toast in the preheated oven for 30 minutes, until puffed and golden brown.

Once baked, remove from the oven and sprinkle light brown sugar evenly over the surface.

Using a kitchen torch, carefully caramelize the brown sugar until bubbly and golden, or place it under the broiler for a few minutes, watching closely to prevent burning.

Allow the crème brûlée French toast to cool for a few minutes, then dust with powdered sugar before serving.