Preparation

Make the bread pudding

• Butter an 8-cup baking dish, such as an 8-inch square. Pile in the bread cubes; the dish should be almost completely filled. Have ready a larger baking pan that can comfortably hold the smaller dish.
• In a medium bowl, whisk the eggs, yolk, sugar, vanilla, and salt. Add the milk and cream, and whisk until well blended. Pour the egg mixture evenly over the bread. Cover with plastic wrap directly on the surface, and let sit at room temperature, pressing down on it occasionally to submerge the bread in the custard, for at least 45 minutes and up to 24 hours. (Refrigerate if soaking for more than 2 hours; let sit at room temperature while the oven heats.)
• Position a rack in the center of the oven and heat the oven to 350°f. Bring a kettle of water to a boil, and then take it off the heat. Remove the plastic wrap from the pudding and place the baking dish in the larger baking pan. Put the baking pan on the oven rack. Carefully pour enough hot water into the pan to reach about halfway up the sides of the baking dish.
• Bake until the center of the pudding springs back when gently pressed with a finger and a knife inserted in the center comes out almost clean, 50 to 55 minutes. Cool in the water bath on a rack for about 15 minutes. Carefully lift the baking dish out of the water and transfer to the rack to cool.

Make the rum-raisin sauce

• Combine the cream, raisins, and sugar in a 3-quart saucepan. Bring to a boil over medium-high heat, reduce the heat to low, and cook, stirring frequently, until the mixture thickly coats a silicone spatula and holds a line drawn through it, 6 to 8 minutes. Off the heat, stir in the rum.

Serve

• Serve the bread pudding warm or at room temperature with warm rum-raisin sauce drizzled over each portion. Serve the extra sauce on the side.

Coconut-Ginger
Scatter 2 Tbs. finely chopped crystallized ginger over the bread cubes. in place of milk and cream in the custard, use two well-shaken 13.4-oz. cans coconut milk. increase the vanilla to 2-1/2 tsp. and add 1-1/4 tsp. finely grated fresh lemon zest to the custard. After baking, sprinkle toasted shredded coconut over the pudding.

Cranberry-Almond
Soak 1/2 cup dried cranberries in very hot tap water until plumped, about 20 minutes. Drain well. Scatter the cranberries over the bread cubes. Add 3/4 tsp. pure almond extract to the custard. After baking, sprinkle toasted sliced almonds over the pudding.

Chocolate-Cherry
Soak 1/2 cup dried cherries in very hot tap water until plumped, about 20 minutes. Drain well. Scatter the cherries and 2 oz. finely chopped bittersweet chocolate over the bread cubes. increase the granulated sugar to 3/4 cup, and whisk 1 oz. (1/3 cup) unsweetened Dutchprocess cocoa powder into the custard.