Preheat the oven: Heat to 400°F (200°C). Line a sheet pan with parchment paper or lightly oil it for easy cleanup.
Make a panade: In a large bowl, combine breadcrumbs and milk. Stir and let it sit 2–3 minutes to soften.
This keeps the meatballs tender.
Add flavor builders: Stir in the grated onion (with juices), garlic, Parmesan, parsley, salt, pepper, and paprika. Mix until evenly combined.
Fold in the chicken and egg: Add ground chicken and the egg to the bowl. Use a fork or your hands to gently mix. Do not overwork the meat or the meatballs will turn dense.
Shape the meatballs: Lightly oil your hands.
Scoop about 1 1/2 tablespoons of mixture and roll into balls about 1 1/4 inches wide. You should get 20–24 meatballs.
Arrange and oil: Place meatballs on the prepared sheet, spaced slightly apart. Brush or drizzle with olive oil for browning.
Bake: Cook for 13–16 minutes, until the centers reach 165°F (74°C) on an instant-read thermometer.
If you want more color, broil for 1–2 minutes at the end.
Rest and serve: Let them rest 3 minutes so juices settle. Serve with marinara over whole-grain pasta, tuck into pitas with greens and yogurt sauce, or pair with roasted veggies and rice.
Pan-sear option: Heat 1–2 tablespoons olive oil in a large skillet over medium heat. Cook meatballs in batches, turning to brown all sides, about 8–10 minutes total, until the centers reach 165°F.