In a large bowl, combine ground chicken, bread crumbs, egg, Parmesan, garlic, parsley, Italian seasoning, onion powder, salt, and pepper. Mix gently with hands until just combined. Shape mixture into tablespoon-sized balls, about 1 to 1.5 inches in diameter. You should get approximately 30 meatballs. Wetting hands slightly prevents sticking.

Melt butter in a large 12-inch skillet over medium-high heat. Once butter stops foaming, add meatballs in a single layer, leaving about 1 inch space between each. Brown on all sides for 6 to 8 minutes total. Transfer to a plate, cover loosely with foil, and set aside. Drain excess fat and wipe skillet clean.

Return clean skillet to medium heat and add 1 tablespoon reserved oil from sun-dried tomatoes. Once shimmering, add minced garlic and cook for 30 seconds, stirring constantly until fragrant. Add tomato paste and cook for 1 minute longer, stirring constantly.

Pour in chicken stock and use a wooden spoon to scrape up all browned bits stuck to bottom of pan.

Reduce heat to medium-low and stir in heavy cream, Parmesan cheese, Italian seasoning, and red pepper flakes if using. Let sauce simmer gently for 2 to 3 minutes until it starts to thicken. Return meatballs to pan along with chopped sun-dried tomatoes. Simmer for 10 to 15 minutes, stirring occasionally, until sauce thickens enough to coat back of spoon and meatballs reach internal temperature of 165°F.

Remove from heat and stir in fresh julienned basil. Taste and adjust seasoning with salt and pepper as needed.