Heat the oven to 350 degrees F (177 degrees C).
Grease an 8 x 6 - inch baking dish with the tablespoon of butter and set aside.
Place the cubes of bread in a large bowl and set aside.
In another bowl, whisk together the eggs, milk, brown sugar, vanilla, cinnamon, nutmeg and salt. Pour over the bread and gently stir to combine.
Allow the mixture to sit at room temperature for 15 minutes.
Transfer the bread mixture to the baking dish and bake until the center of the bread pudding is set, 45 to 50 minutes.
While the bread pudding is baking, make the whiskey sauce.
In a medium saucepan set over medium heat, combine the cream, milk and sugar. Add the cornstarch and the whiskey to a small mixing bowl and whisk to blend until smooth.
Pour the whiskey mixture into the cream mixture and bring to a boil.
Once the sauce begins to boil, reduce the heat to a gentle simmer and cook, stirring occasionally, for 5 minutes.
Remove the sauce from the heat, add the salt and stir in the butter.
After the bread pudding has finished baking, remove from the oven and pour Whiskey Sauce over the top.