Heat oven to 400°F. Line a sheet pan with parchment and lightly brush with olive oil.
Stir breadcrumbs and milk in a large bowl. Let the mixture soak for 2 minutes.
Add ground chicken, beaten egg, 1/2 cup Parmesan, garlic, onion, parsley, Italian seasoning, salt, and pepper. Mix gently until just combined.
Divide into 6 equal portions. Shape into small loaves and place on the prepared pan. Brush tops with olive oil.
Bake 18–20 minutes, until the centers reach 165°F on an instant-read thermometer.
Combine melted butter, remaining Parmesan, and garlic powder. Brush over hot meatloaves; broil 1–2 minutes to brown, if desired.
Rest 5 minutes before serving so the juices settle.