Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish.

In a large mixing bowl, set aside the cubed day-old bread.

In another bowl, whisk together eggs, whole milk, heavy cream, granulated sugar, whiskey, vanilla extract, ground cinnamon, and salt until smooth.

Pour the custard mixture over the bread cubes and gently stir to soak all the cubes.

Let the mixture rest for about 15 minutes to allow the bread to absorb the custard.

Transfer the soaked bread mixture into the greased baking dish and spread evenly.

Bake for 30 to 45 minutes until golden brown and set.

Cool for 15 to 20 minutes before serving.

Drizzle with warm caramel sauce and add whipped cream if desired.