Preheat oven to 375°F. Set out an 8x8-inch (2-quart) baking dish.
Quarter the brioche slices.
In a large bowl, combine all custard ingredients. Whisk until smooth. Gradually drizzle in 3 tablespoons of melted butter, whisking continuously. It’s okay if the butter clumps slightly.
Add bread quarters to the custard. Gently fold to ensure each piece is coated. Let stand 3 minutes.
Transfer bread and custard mixture to the baking dish. Press into an even layer. Use a pastry brush to brush (or drizzle on) the remaining 2 tablespoons melted butter evenly on top. Bake 40–45 minutes or until the top is lightly golden and the center is set but slightly wobbly. Be careful not to overbake.
Rest for a few minutes, then serve with one of the below options (my fave is option 2!):Option 1: Sprinkle powdered sugar on top and enjoy as is.Option 2: Prepare caramel sauce (see note 2 for ingredients). Add everything to a small pot over medium-low heat and whisk until smooth. Bring to a boil, then reduce heat and cook until thickened. Remove from heat and whisk. Prepare whipped cream: combine everything (see note 3) in a stand mixer and whisk until soft peaks form. Spoon whipped cream over warm bread pudding then drizzle caramel sauce on top.Option 3: Make crème anglaise: when starting to prepare the dessert, set out pint of ice cream and allow to fully melt. Stir, then drizzle over bread pudding.Option 4: Serve with a scoop of vanilla bean ice cream.
Notes
Note 1: Opt for bakery-quality brioche bread for the best results—the quality of bread enhances the pudding! Use approximately 15-1/2 ounces or 13 slices, each cut about 3/4 inch thick, amounting to about 10 cups when gently packed.Note 2: These are the ingredients to make caramel sauce: 1/2 cup butter, 1 cup brown sugar, 1/2 cup heavy cream, 1/8 tsp salt, and 1 tsp vanilla.Note 3: These are the ingredients to make whipped cream: 1 cup heavy cream, 2–4 tbsp powdered sugar, 1 tsp vanilla, and a tiny pinch of salt.Storage: To store, cool completely after baking, cover tightly, and refrigerate for up to 3 days. To freeze, bake in a foil pan, cool, and wrap tightly with storage wrap and foil. Freeze for up to 3 months. Freeze extra sauce separately.