Grease a 9x13 inch baking dish with butter. Arrange half of the bread cubes in the bottom of the dish.
Toss the chopped apples with 2 tablespoons of brown sugar and 1 teaspoon of cinnamon. Scatter half the apples over the bread.
Layer the remaining bread and then the remaining apples on top.
Whisk together eggs, milk, heavy cream, vanilla, remaining brown sugar, and 1 tablespoon of cinnamon in a large bowl.
Pour the egg mixture evenly over the casserole. Press down gently with a spatula.
Cover with foil and refrigerate overnight (or at least 4 hours).
Preheat oven to 350°F (175°C). Remove casserole from fridge to take the chill off.
Mix flour, a pinch of brown sugar, cinnamon, and cold butter until crumbly. Sprinkle over the top.
Bake for 45-55 minutes until the center is set and the top is golden brown.
