Put the torn challah pieces into the prepared baking dish. In the small bowl, soak the raisins in hot water until soft, about 5 minutes, then drain well. Sprinkle the raisins and walnuts on the torn challah, tossing lightly to get some under the top layer.
In the large mixing bowl, whisk together the apple butter, whole milk, and eggs. Pour over the challah and spread to make sure all of the bread is covered.
Bake in the preheated oven until cooked all the way through and a toothpick tester comes out clean, about 30 minutes. Allow to cool on a wire rack, and serve warm.