Grease a 9×13″ baking dish.

Arrange half the cubed bread in the dish; top with half the apples.

Whisk together eggs, milk, heavy cream, granulated sugar, vanilla, cinnamon, and nutmeg.

Pour half this mixture over the bread and apples.

Top with remaining bread and apples, then pour over the rest of the custard mixture. Press gently so bread absorbs liquid.

Cover and refrigerate overnight (or at least 4 hours).

Preheat oven to 350 °F (175 °C). Uncover casserole and bake 35–45 minutes until puffed and golden.

Meanwhile, make apple–caramel syrup: melt butter in a saucepan, add brown sugar and heavy cream, bring to gentle boil with apple slices, cook 1 minute until saucy.

Remove casserole from oven, let sit 5 minutes, then drizzle apple–caramel syrup over top.

Serve warm, optionally topped with whipped cream or extra caramel.