1. Make the meatballs by mixing all ingredients with your hands. Form into golfball-size meatballs and bake at 350 degrees F for 30 minutes.
2. While the meatballs are baking, make the fondue. Add the butter to a small saucepan over medium heat and melt. Whisk in the flour and cook for 1 minute.
3. Stir in the mustard, Worcestershire, and beer. Whisk constantly until mixture has thickened, about 2 minutes.
4. Remove from heat and stir in the grated cheddar cheese. Continue stirring until sauce is smooth and creamy.
5. Pour into a fondue pot or small crockpot to serve, alongside burger accoutrements and long toothpicks or fondue picks. Enjoy!