Preheat your oven to 375°F (190°C). Line a baking sheet with parchment paper or foil for easy cleanup.

In a large mixing bowl, combine the ground chicken, panko breadcrumbs, 1/4 cup grated Parmesan cheese, 2 cloves minced garlic, 1/4 cup finely chopped fresh parsley, lightly beaten egg, milk, onion powder, salt, and black pepper.

Mix gently with your hands or a spatula until just combined. Be careful not to overmix, as this can result in tough meatloaves.

Divide the chicken mixture into 4 equal portions. Shape each portion into a small, loaf-like shape, approximately 4-5 inches long and 2-3 inches wide. Place them evenly spaced on the prepared baking sheet.

Bake in the preheated oven for 20 minutes.

While the meatloaves are baking, prepare the glaze. In a small saucepan over low heat or in a microwave-safe bowl, melt the unsalted butter. Stir in the remaining 2 cloves minced garlic, 2 tbsp grated Parmesan cheese, 1 tbsp chopped fresh parsley, and the optional red pepper flakes.

After 20 minutes of baking, carefully remove the meatloaves from the oven. Brush the garlic Parmesan glaze generously over the top and sides of each meatloaf.

Return the glazed meatloaves to the oven and bake for another 10-15 minutes, or until the internal temperature reaches 165°F (74°C) when measured with a meat thermometer, and they are lightly golden brown.

Remove from the oven and let the meatloaves rest on the baking sheet for 5 minutes before serving. This allows the juices to redistribute, ensuring moist and flavorful meatloaves.