Preheat the oven to 300 degrees F. Wrap the hot dog rolls in foil. In a large skillet, cook the beef, half of the onions and the garlic over medium-high heat, breaking up the meat, until the onions are softened and the meat is cooked though, about 5 minutes. Stir in the chili powder and cumin and cook, stirring occasionally, for 3 minutes. Stir in 1 cup water, the tomato paste, mustard, Worcestershire sauce and brown sugar. Bring to a boil, then cover, reduce the heat to medium and cook until thickened, about 20 minutes.
Meanwhile, in a large saucepan, cover the hot dogs with water and bring to a boil. Cook until heated through, about 8 minutes. Place the rolls in the oven and heat through. Place the hot dogs in the rolls and top with the chili, the remaining onions and extra mustard.