Step 1

Make matzo balls: Using a small spoon, gently scrape away any fat that has solidified on surface of broth. Warm 1/4 cup fat in the microwave, reserve remainder for another use. In a large bowl, whisk together fat, 1/4 cup broth, egg yolks, salt and pepper. Whisk in seltzer, and immediately fold in matzo meal. In a separate bowl, with a mixer, whip egg whites until stiff peaks form. In batches egg whites into matzo meal until just incorporated; refrigerate 20 minutes.

Step 2

Bring a large pot of lightly salted water to a boil. Wet hands, form matzo mixture into 1 1/2-inch balls, and drop into boiling water. Reduce to a simmer, cover, and cook until matzo balls are puffed and tender, 25 to 30 minutes. Meanwhile, in a medium pot, bring 8 cups broth to a simmer. Season with salt. Add sliced carrots and simmer until tender, about 7 minutes. With a slotted spoon, remove matzo balls from water and divide among four bowls. Ladle broth and carrots into bowls and top with dill springs.