Preheat your oven to 350°F (175°C). Grease a baking dish (around 9x13 inches works well).
In a large bowl, whisk together the eggs, milk, cream, sugar, vanilla, cinnamon, and salt.
Arrange the brioche slices in the baking dish. Pour the custard evenly over the bread, making sure each slice is coated. Let it soak for about 10 minutes so the bread absorbs the mixture.
Drizzle the melted butter over the top. Bake for 30–35 minutes, until golden brown and the center is set.
While the French toast bakes, prepare the toppings:For the bananas: heat 1 tablespoon butter and 1 tablespoon sugar in a skillet over medium heat. Add banana slices and cook until golden and caramelized on both sides (careful when flipping over, they will break easily) For the mascarpone: whisk together mascarpone and vanilla extract until smooth and creamy.
Wash and cut the fresh strawberries, if using.
Remove the baked French toast from the oven. Serve warm, topped with a dusting of powdered sugar. Serve with the caramelized bananas, vanilla mascarpone and fresh berries.