Soak the raisins. Place the raisins in a small bowl and pour the rum over them. Warm gently in the microwave for 30 seconds or on the stove until just warm. Let them soak for at least 20–30 minutes so they plump up.

Prep the bread. Cut day-old bread into 1-inch cubes. If it’s fresh, spread cubes on a baking sheet and toast at 300°F (150°C) for 8–10 minutes to dry them slightly. This helps the custard absorb evenly.

Heat the oven. Preheat to 350°F (175°C). Grease a 9x13-inch baking dish with butter.

Make the custard. In a large bowl, whisk together milk, cream, eggs, granulated sugar, brown sugar, vanilla, cinnamon, nutmeg, and salt until smooth.

Combine. Add the bread cubes to the bowl and toss gently to coat. Let the mixture sit for 10–15 minutes so the bread absorbs the custard. Stir once or twice.

Add raisins. Drain the raisins (reserve any leftover rum for sauce, if you like). Fold the raisins into the soaked bread mixture.

Assemble. Pour everything into the prepared dish. Dot the top with small pieces of butter for extra browning and flavor.

Bake. Bake for 40–50 minutes, until the top is golden and the center is just set. A knife inserted near the center should come out mostly clean with a little moisture.

Rest and serve. Let it cool for 10–15 minutes before serving. Serve warm as is, or add a quick rum butter sauce.

Optional rum butter sauce. Melt 4 tablespoons butter in a small saucepan. Whisk in 1/2 cup powdered sugar and 2–3 tablespoons cream until smooth. Off the heat, stir in 1–2 tablespoons rum and a pinch of salt. Drizzle over warm pudding.