One 8-ounce container Greek yogurt or plain whole milk yogurt
1 tablespoon milk
Preheat the broiler. Brush a rimmed baking sheet with the olive oil.
In a large bowl, combine the lamb with the onion, bread crumbs, eggs, mint, lemon juice, cinnamon, 1 tablespoon of the dill, 2 teaspoons of the garlic and 1 teaspoon of salt; knead until combined. Form the mixture into 1 1/4-inch meatballs. Arrange the meatballs on the oiled baking sheet and broil as close to the heat as possible for 6 minutes, turning the pan halfway through, until firm and lightly browned.
Meanwhile, in a small bowl, whisk the yogurt with the remaining 3 tablespoons of dill and 2 teaspoons of garlic; whisk in the milk and season with salt. Transfer the meatballs to a plate and serve with the sauce.
The recipe can be prepared up to 1 day ahead. Reheat the meatballs before serving.