Cut a loaf of sourdough bread into cubes.
In a bowl mix eggs, milk, heavy cream, sugar, and salt. Whisk until well combined
Place bread cubes in a greased 9x13 inch buttered casserole dish and pour egg mixture evenly over them. Cover with plastic wrap and refrigerate overnight.
In a small bowl, mix together flour, brown sugar, cinnamon, and salt. Cut in butter until the mixture resembles breadcrumbs. Store in an airtight container or a ziplock bag and also refrigerate overnight.
preheat oven to 350F
Take the baking dish out of the fridge and evenly sprinkle topping over bread mixture.
Bake for 45 mins or until the top is slightly brown and the toothpick comes out clean.