Preheat your oven to 375°F.

In a large bowl, whisk together both sugars, melted butter, vanilla extract, cinnamon, and salt.

Add the eggs to the sugar mixture and whisk until well combined.

Pour in the milk and heavy cream, and whisk until the mixture is smooth.

Place the cubed bread in a separate large bowl and pour the egg mixture over the bread, ensuring all pieces are coated.

Transfer the bread mixture to a 2.5-quart casserole dish, spreading it out evenly.

Dot the top with cold butter pieces and, if desired, sprinkle with turbinado sugar for a sweet, crunchy topping.

Bake on the center rack of the oven for 50-55 minutes, until the top is browned and the center is slightly jiggly.

Allow the bread pudding to cool slightly before serving.