Cut bread into 1-inch cubes and scatter evenly in a greased 9-x-13-inch baking dish.

In a medium bowl, mix eggs, milk, heavy cream, vanilla, and sugar together, then pour evenly over the bread.

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

To make the topping, mix flour, brown sugar, cinnamon, and salt in a medium bowl. Cut butter into this mixture until crumbly. Place the topping in a small resealable plastic bag and refrigerate overnight as well.

When ready to bake, preheat the oven to 350°F.

Unwrap the baking dish and sprinkle the topping evenly over the bread.

Bake, uncovered, for 45-60 minutes, depending on how soft you like it.