Cut the thick bread into 1-inch cubes and place them in a greased 9x13-inch baking dish.

In a large mixing bowl, whisk together the eggs, whole milk, heavy cream, granulated sugar, vanilla extract, ground cinnamon, and salt until smooth.

Pour the egg mixture over the bread cubes, ensuring all pieces are covered. Press down gently and cover with aluminum foil. Chill in the refrigerator for at least 30 minutes or overnight.

Preheat the oven to 350°F. Bake the casserole covered for 30 minutes, then remove the foil and bake for an additional 15-20 minutes until golden brown.

Warm the maple syrup in a small saucepan. Drizzle over the baked casserole and serve warm.