In a small saucepan set over medium heat, combine cranberries, raisins, and rum. Bring to a boil, then remove from heat and set aside to allow the fruit to steep while you prepare the bread pudding.
Butter a 2-quart casserole pan. Place cubed French bread in a large bowl. Drizzle melted butter over bread and toss to coat. Transfer bread cubes to prepared casserole pan and set aside.
In a large saucepan set over medium heat, combine eggnog and milk/cream. Bring to a low boil, whisking occasionally, then remove from heat.
In the same bowl you tossed the bread cubes in, whisk together eggs, sugar, nutmeg, vanilla, and salt until light and frothy. Slowly whisk 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 liquid to ensure every piece is soaked. Scatter prepared cranberries and raisins over top, then sprinkle with turbinado sugar. Cover pan with plastic wrap and refrigerate 2-24 hours.
When ready to serve, preheat oven to 350 degrees F. Remove pudding from refrigerator and unwrap. When oven is ready, bake on middle rack for 45-55 minutes until top is browned, edges pull away from pan easily, and there is no wet jiggle in the middle.
Remove from oven and allow to cool 20-30 minutes before serving,
Warm Whiskey SauceCombine sugar, cream, and butter in a small saucepan set over medium heat. Bring to a low boil, whisking occasionally. Remove from heat and whisk in whiskey and vanilla until combined. Cool 10 minutes, then drizzle that glorious sauce over plated bread pudding slices. Enjoy!