In a large skillet or saucepan over medium heat, cook the ground beef and beef heart (if using). Stir frequently, breaking it up into very fine crumbles. The texture is key—use a potato masher or immersion blender for an extra-smooth consistency.
Once the beef is browned and no longer pink, add onions and garlic. Cook for 2-3 minutes until softened. Stir in the tomato paste, allowing it to caramelize slightly for a deeper flavor.
Mix in the chili powder, paprika, cumin, coriander, celery salt, black pepper, and cayenne (if using). Stir well. Then, add the mustard, Worcestershire sauce, apple cider vinegar, and water (or beef broth). Bring to a low simmer.
Reduce the heat to low and let the sauce simmer uncovered for 30-45 minutes, stirring occasionally. The sauce should thicken but remain spoonable. If it gets too thick, add a little more broth or water.
Taste and adjust seasoning if needed. The chili should have a tangy, savory, slightly spicy depth that enhances the hot dog.
