Crock-Pot S'mores Cake

Name: Crock-Pot S'mores Cake
Prep time: 5 min
Total time: 5 min
Cuisine: American
Ingredients: 1 box Devil's Food Cake mix; 1 (4-oz.) package instant chocolate pudding; 1 c. whole milk; 3 large eggs; 1/2 c. (1 stick) butter, melted; 1/4 c. sour cream; 1 tsp. pure vanilla extract; 1/2 tsp. kosher salt; 2 (2-oz.) Hershey bars, broken into smaller pieces; 4 graham crackers, crushed; Cooking spray; 3 c. mini marshmallows; 1/4 c. melted chocolate, for garnish