Preparation: Grease the bottom and sides of a 6-quart slow cooker with butter or cooking spray.
Egg Mixture: In a large bowl, combine the eggs, milk, cinnamon, sugar, and vanilla. Whisk until well mixed.
Dunking Buns: Dunk the hamburger buns into the egg mixture, ensuring they are well coated.
Layering: Place the soaked buns at the bottom of the slow cooker.
Pouring Mixture: Pour any remaining egg mixture over the buns.
Cooking: Cover the slow cooker and cook on low for 5 hours or on high for 3 hours until the buns are golden.
Serving: Serve the French toast with butter and maple syrup.
