1 very large parsley root or 4 medium, or 3 large yukon gold potatoes, peeled and cut into uniform 1/2″ chunks 8 tablespoons butter, divided 1 ½ pounds ground beef 1 ½ red onions, diced 4 – 5 carrots, peeled and cut into half moons 5 stalks celery, sliced 2 teaspoons sea salt, divided 2 teaspoons Worcestershire sauce 1 teaspoon yellow mustard seed 4 bay leaves fresh ground black pepper to taste 6 large leaves kale, cut into thin ribbons