Using a small saucepan set over medium heat, combine cranberries and rum.
Bring to a boil, then remove from heat and set aside to allow the fruit to steep while you make the bread pudding.
Spray a loaf pan with non-stick baking spray and set aside.
In a large bowl place the cubed French bread and set aside.
Drizzle melted butter over bread and mix french bread to coat.
Scoop the french bread into loaf pan and set aside.
Using a large saucepan set over medium heat, combine eggnog and milk.
Bring to a low boil, while whisking occasionally, then remove from heat.
In a large bowl, whisk together eggs, sugar, nutmeg, vanilla, and salt until light and frothy.
Slowly whisk in 1 cup of hot eggnog mixture into egg mixture to temper and avoid scrambling.
Gradually whisk in remaining eggnog mixture until well combined.
Strain rum from fruit into eggnog mixture and whisk to combine.
Pour eggnog mixture evenly over bread cubes, pressing bread down into the liquid to ensure every piece is soaked.
Randomly place cranberries into the bread pudding.
Place into the fridge for 4 hours so that the pudding can soak into the bread.
Preheat oven to 350 degrees F.
Place the loaf pan on middle rack and bake for 45–55 minutes until top is browned, edges pull away from pan easily, and there is no wet jiggle in the middle.
Start making the whiskey sauce during the last 10 minutes of baking time on the bread pudding.
Once baked, remove from oven and allow to cool 20–30 minutes.
Using a small saucepan, combine the sugar, heavy cream, butter, and place over medium heat.
While whisking occasionally, bring the mixture to a low boil.
Remove from stovetop and whisk in the whiskey and vanilla.
Allow sauce to cool for 15–20 minutes.
Remove bread pudding from loaf pan and cut into slices.
Drizzle the sauce onto the slices and serve with fresh whipped cream.