Step 1

Preheat the oven to 300 degrees F. Grease an 8-inch square baking dish with the butter.

Step 2

Toast the bread cubes on a baking sheet until they start to dry and harden, about 20 minutes. Set aside. Raise the oven temperature to 325 degrees F.

Step 3

Whisk together the cream, milk, sugar, vanilla, salt, cinnamon, whole eggs and yolks in a large bowl. Add the bread to the bowl and stir until completely coated. Cover and let soak for about 30 minutes, pushing the bread down occasionally so that all the cubes are soaked. Meanwhile, pour hot water over the raisins, if using, and soak for 10 minutes. Once plumped, drain the raisins, add to the bowl of bread and gently toss.

Step 4

Pour the bread mixture into the prepared baking dish and bake until the custard is set and the top is golden brown, about 1 hour and 30 minutes. Let cool slightly before serving. Serve warm, at room temperature or cold.