Meatballs w/ Egg & Lemon Sauce

1-1/2 pounds ground lamb or beef
1/2 cup long-grain rice
1/2 cup minced onion
1 egg
2 tablespoons tomato sauce
1/4 cup chopped fresh parsley
1/2 teaspoon dried oregano
Salt, freshly ground pepper
2 cups beef bouillon
2 tablespoons unsalted butter
3 egg yolks
1/4 cup fresh lemon juice

In a large bowl combine the lamb or beef, rice, onion, egg, tomato sauce, parsley, and oregano. Season with salt and pepper. Mix well. Shape into 2-inch meatballs. In a large saucepan bring the bouillon to a boil over medium-high heat. Add meatballs and butter. Reduce the heat to medium-low. Cook, covered, until meatballs are tender, about 30 minutes. Test one to see if rice is tender. Meanwhile, in a small bowl beat the egg yolks. Stir in lemon juice. Add 1/2 cup hot liquid; mix well. Add to meatballs, stirring constantly while adding. Leave over low heat about 5 minutes, long enough to thicken a little. Serve at once. Do not reheat.