Lightly coat the inside of a 4-quart slow cooker with cooking spray. Spread challah in one layer on a sheet pan; dry out in a 350°F oven for about 10 minutes. Let cool.
Mix together challah, dried fruit, and chocolate chips in a large bowl. Transfer to slow cooker. Whisk together half-and-half, yolks, Nutella, sugar, and vanilla in the bowl until well combined. Pour over bread in slow cooker and press gently so the mixture seeps in. Cover and cook on low until set, 2 1/2 to 3 hours. Let cool 15 minutes before serving.
Spoon bread pudding into bowls and top with whipped cream.