Preheat oven to 425°F. Line a rimmed sheet pan with parchment and lightly oil it.
Stir breadcrumbs and milk in a small bowl. Let soak 2 minutes.
Combine chicken, egg, scallions, celery, garlic, parsley, salt, pepper, onion powder, and paprika in a large bowl.
Add the soaked breadcrumbs to the chicken mixture. Mix gently until just combined.
Scoop and roll 1.5-inch meatballs (about 24). Arrange on the pan and brush tops with a little oil.
Bake 14 minutes, until the centers are nearly cooked through.
Meanwhile, melt butter in a saucepan. Whisk in hot sauce, honey, and garlic powder. Keep warm.
Transfer meatballs to a bowl and pour the warm Buffalo sauce over them. Toss to coat well.
Return sauced meatballs to the pan. Bake 4 minutes to set the glaze. Sprinkle blue cheese if using.