Preheat your oven to 425°F (215°C).
In a large mixing bowl, stir together the panko and milk or buttermilk and set it aside for a few minutes to allow the panko to absorb the liquid.
½ cup panko, 2 tablespoons buttermilk
Add the crumbled feta, minced garlic, chopped herbs, chopped olives, lemon zest, and black pepper and stir together.
¼ cup Kalamata or other black olives, ¼ cup feta, crumbled, 1 clove garlic, minced, 2 tablespoons fresh herbs, chopped, 1 teaspoon lemon zest, ¼ teaspoon ground black pepper
Add the ground chicken and the egg, and use your hands gently to mix everything together until well combined.
1 pound ground chicken, 1 egg
Using a medium (#40) cookie scoop or your hands, form the mixture into about 1½ inch meatballs and place them on a baking sheet lined with parchment paper.
Bake the meatballs in the preheated oven for about 15 minutes, turning them over once or twice for even browning. They should be cooked to 165℉ (74℃) and turning golden brown on the outside. Serve immediately.