Here is the original recipe from The Washington Post. I substituted butter for margarine and left out the chives. So delicious!
Leek-Parsley Matzoh Balls
adapted from a recipe in The Washington Post, March 24, 2010
MAKE AHEAD: The matzoh ball mixture needs to rest in the refrigerator for at least 2 hours and up to 1 day; uncooked balls need to rest for 30 minutes in the fridge before they are cooked. The cooked matzoh balls can be refrigerated in or out of liquid up to 3 days in advance. Reheat in your favorite broth, over low heat, until warmed through.
Makes 14 to 16 medium-size balls or about 30 small balls
6 tablespoons unsalted butter
1 medium leek, white and light-green parts only, cleaned, then finely chopped (1/2 cup)
Large handful of flat-leaf parsley leaves, finely chopped (1/2 cup)
4 large eggs
1 1/4 cups plain matzoh meal, preferably Streit's
1/2 cup plain club soda or plain seltzer water
1/2 to 1 teaspoon salt
1/4 teaspoon freshly ground black pepper
Melt the margarine or butter substitute in a small skillet over medium heat. Add the leek and cook for 5 minutes, until softened. Remove from the heat; add the parsley.
Beat the eggs in the bowl of a stand mixer or hand-held electric mixer on medium speed for about 2 minutes, until frothy.
Stir in the leek-parsley mixture. Gradually add the matzoh meal, then stir in the club soda and mix well; the consistency should be like that of corn muffin batter. Add salt to taste and the pepper. Cover with plastic wrap and refrigerate for at least 2 hours and up to 1 day.
Line a baking sheet with plastic wrap. Wet the palms of your hands and form either 14 to 16 medium balls or 30 small balls (small ones will be a generous teaspoon). Do not compress; work your fingers gingerly around the ball in shaping it as round and smooth as possible. Place the completed balls on the baking sheet as you work. Cover loosely with plastic wrap and refrigerate for 30 minutes.
Meanwhile, bring a large pot of salted water to a boil over high heat. Working in batches as needed (no more than 10 to a very large pot), drop the balls into the water; reduce the heat to medium, partially cover and cook for 40 to 60 minutes, until the balls are tender. Transfer the cooked matzoh balls to a bowl and cover loosely to keep warm while you cook the remaining matzoh balls. Add to your favorite warm broth, or cool and refrigerate as directed above.