In a large bowl, whisk the eggs, milk, heavy cream, granulated sugar, vanilla extract, and ½ teaspoon of cinnamon.
Cut the bread into one inch squares and toss into the egg mixture until all the squares are soaked in it. Cover with plastic wrap and refrigerate for 3 hours or overnight.
Preheat the oven to 350 F. Make the topping: in a small bowl combine the flour, brown sugar, 1 ½ teaspoons cinnamon, and a pinch of salt. Cut the butter into the sugar mixture until it resembles sand.
Grease a 9x13-inch casserole dish and spoon the bread/egg mixture into the dish.
Sprinkle the topping evenly over the bread and bake for 50 mins or until golden on top and the egg is fully cooked. Drizzle with the powdered sugar glaze and serve hot.