Preheat the oven to 375°F (190°C). Butter an 8-inch (20 cm) square baking dish with 2 teaspoons of butter and set out a larger baking dish that will hold it with some space around the sides.
In a large bowl, whisk together the milk, sugar, egg yolks, egg, and vanilla until smooth.
Add the cubed bread and raisins. Stir gently and let soak for 15 minutes, stirring once halfway through.
Transfer the soaked bread and any remaining custard to the buttered dish. Gently spread the bread and raisins into an even layer. Place the dish of bread pudding inside the larger dish. Pour hot water into the larger dish until it reaches halfway up the sides of the bread pudding.
Carefully transfer both baking dishes to the oven, keeping the smaller dish inside the larger water-filled dish. Bake uncovered for 50 to 55 minutes, or until golden and the custard is set. A slight wobble in the centre is fine, but there shouldn't be any visible liquid custard. Carefully remove the smaller dish from the water bath and let cool slightly on a wire rack.
Make the rum sauce:
While the pudding bakes, whisk together the brown sugar and cornstarch in a small saucepan. Add the cold water a little at a time, whisking continuously until smooth.
Bring to a gentle boil over medium heat, whisking often, and cook for about 2 minutes, or until the sauce thickens to the consistency of maple syrup. Remove from the heat and whisk in the rum, butter, and vanilla. Spoon the warm rum sauce over individual servings of bread pudding.
Notes
For detailed ingredient notes, substitution tips, variations, and step-by-step photos, scroll through the full recipe post.
Use a digital kitchen scale for precise measurements and an oven thermometer to confirm your oven is heating correctly.
To switch to gram measurements, click "Metric grams" in the ingredients section of the recipe card.
When choosing a larger baking dish for the water bath, use an outer baking dish large enough to leave room for water around the smaller dish.
Use ¼ cup (40 g) of raisins for a lighter scattering throughout the pudding, or increase to ½ cup (80 g) if you like more.
A little goes a long way with this bread pudding, especially once you add the rum sauce. Six servings may not look like much, but it's quite a rich dessert.
The finished sauce still contains alcohol. Removing the saucepan from the heat before adding rum doesn't cook that alcohol away.
Storage
Refrigerate leftover bread pudding and rum sauce separately in airtight containers within two hours of cooking. Store for up to 3 to 4 days.
I reheat individual portions of bread pudding in the microwave in short intervals until heated through. You can reheat with or without sauce on top.
For longer storage, freeze the bread pudding without sauce in an airtight, freezer-safe container for up to 1 month. Thaw overnight in the refrigerator before reheating.