- In a non-stick skillet over medium heat, brown the onions in the butter for about 15 minutes. Season with salt and pepper. Deglaze with 1 tbsp (15 ml) of the vinegar. Set aside.
- Preheat the grill, setting the burners to high. Oil the grate.
- Reduce the heat to medium. Grill the sausages for 8 to 10 minutes or until cooked through, turning them frequently. Toast the hot dog buns.
- Meanwhile, in a small bowl, combine the parsley with the remaining vinegar and the oil. Season with salt and pepper.
- Spread the hot dog buns with mustard. Fill each bun with a sausage and top with caramelized onions and the parsley mixture. Serve with a green salad, if desired.