Matzo Ball Soup

For Schmaltz: Season chicken wings with salt and place them in a single layer in a large ovenproof dutch oven (6-8 qt). Roast for 45 minutes or until the fat has rendered (about ¼ cup) at 450°F. Pour the schmaltz into a bowl to cool.
Make broth: Transfer the chicken wings and onion halves to a pot. Add 6 cups of water. Simmer the broth slowly at low heat for 4-6 hours on the stove, or 30 minutes at high pressure in an instant pot, or 8 hours at low heat in a crock pot. Strain the broth and set aside.
Make Matzo balls: Gently mix all matzo balls ingredients in a bowl. Do not overmix.
Cover and refrigerate for 30 minutes or up to 24 hours. With wet hands, shape the mixture into balls before cooking.
In a large pot, add broth, diced carrots, celery, and extra water if necessary. Season with salt/pepper. Bring to a boil over medium-high heat.
Gently drop matzo balls into the broth. Cover the pot, simmer on low heat for about 30-40 minutes for al dente, or longer for lighter texture. Serve with chopped parsley.