Adapted from Ina Garten
4 extra-large eggs, separated
1/2 cup good chicken stock
1/4 cup chicken fat, melted (skim this from the top of the homemade soup)
1/2 cup minced fresh parsley (optional for those who do not like anything green in their matzah ball)
2 teaspoons kosher salt, plus more for egg whites
1 cup matzah meal
1 tablespoon seltzer
Whisk together the egg yolks, chicken stock, chicken fat, parsley, seltzer and salt. Stir in the matzah meal. In the bowl of an electric mixer with a whisk attachment, whip the egg whites with a pinch of salt until they are stiff. Whisk them into the matzah mixture until it is smooth. Refrigerate for at least 30 minutes, or until the mixture is thick.
Form balls the size of golf balls by rolling them in the wet palm of your hand, or scooping them with a small ice cream scoop. Handle them gently and do not use force (the more they are handled the tougher they become). Drop them into simmering chicken stock and cook for 30 minutes, or until fully cooked and puffed, turning once. Remove and serve hot in chicken soup.