If the raisin bread is starting to get hard/stale, skip the first step.
If the raisin bread is still soft, preheat the oven to 300°F and cut 16 ounces raisin bread into 1-inch pieces. Place the pieces on a large baking sheet (or two). Bake for 10–15 minutes, or until lightly golden brown.
Grease a 9x13-inch baking dish.
Whisk together 2 cups milk, ½ cup melted butter, 5 eggs, ¼ cup sugar, 2 teaspoons cinnamon, and 1 teaspoon vanilla.
Place the toasted bread pieces into prepared baking dish. Pour the milk mixture over the top. Gently press the bread cubes so they are all covered with the milk mixture.
Bake at 325°F for 1 hour, or until a toothpick inserted into the center comes out clean.
Dust with powdered sugar. Serve topped with ice cream or whipped cream.
Notes
You can easily halve this recipe and bake it in an 8x8-inch pan for 45–50 minutes. Tap the ".5X" button next to the Ingredients above and it'll halve the recipe for you. If you don't have 16 ounces of raisin bread, you can do a mixture of raisin bread and another bread (like white bread, ciabatta, brioche, etc.). If you'd like the bread pudding to be sweeter on its own, increase the sugar to ½ cup. I found that the ¼ cup sugar in the recipe was plenty if adding whipped cream or ice cream on top. Store any leftovers in the fridge. Reheat in the microwave or oven.