In a large mixing bowl, combine 1 pound of ground beef, the finely grated onion, uncooked arborio rice, freshly chopped parsley, and dill. Add one egg along with salt, pepper, and a sprinkle of oregano. Mix gently using your hands until just combined.

Take small amounts of the mixture—about the size of golf balls—and shape them into uniform meatballs. Place them on a plate lined with parchment paper. Chill in the refrigerator for 15 to 20 minutes.

In a wide pot, pour in the chicken broth and a drizzle of olive oil, then bring to a gentle simmer. Carefully add the chilled meatballs, cover, reduce heat to low, and let simmer for about 30 minutes.

While the meatballs are cooking, whisk together the eggs and lemon juice until well combined. Gradually temper this mixture with about 1 cup of the hot broth from the pot.

After the meatballs are done cooking, lower the heat and slowly pour the tempered avgolemono sauce back into the pot, stirring gently to mix.

Once the sauce has reached desired consistency, serve warm, garnished with extra dill or lemon wedges.