In a large bowl, whisk together sugar, brown sugar, eggs, cream, milk, bourbon, salt, and vanilla. Whisk until the sugar has dissolved.
Spread bread in 9 x 12-inch pan. Add chocolate chips and walnuts. Toss to combine until well distributed. Pour liquid mixture over bread. Gently push bread down to ensure it get coated with liquid. Cover pan and let chill in the fridge for at least one hour, or up to overnight.
Preheat oven to 350 degrees F. Bake for 40-50 minutes until the liquid has set and the top pieces of bread are toasty. Let bread pudding sit for 10 minutes to slightly cool. Serve bread pudding warm with caramel sauce.
Brioche is recommended, but you can pretty much use any bread. Any and all breads can be used for bread pudding: baguettes, brioche, croissants, even doughnuts! Usually day-old bread (lightly stale) is preferred because it is better suited to soaking up the liquids.
Bourbon adds a touch of warmth and flavor. Dark rum or flavored liquor such as Frangelico (hazelnut liqueur) or Amaretto (almond liqueur) are other options.
Adding alcohol is optional. If you omit alcohol, sub in with additional milk or heavy cream.