Stir the white chocolate chips, pudding mix, and sour cream into the prepared cake batter.

Spray a 3-quart or larger slow cooker with butter-flavored cooking spray, and then pour the batter into it. Cover and cook on high for about 2 hours, and then stir well.

Cover and cook on high for another 1 1/2 hours or until the dessert is mostly set in the middle and firm around the edges. The top and middle will still be a little goey.

Turn off slow cooker and let it sit for at least 30 minutes. The dessert will have a consistency of a bread pudding.

Spoon into bowls and serve with vanilla ice cream