Preheat oven to 450°F (235°C). Line a baking sheet with parchment paper.
In a bowl, soak breadcrumbs in milk for 2 minutes.
Use a food processor to finely chop onion, garlic, parsley, and sun-dried tomatoes. Combine with ground chicken, soaked breadcrumbs, ricotta, egg, Parmesan, Italian seasoning, and salt in a large bowl.
Shape into 18-20 (2.5-inch) meatballs and place on the baking sheet. Spray with cooking oil.
Bake for 15-20 minutes until crisp and cooked through.
For the sauce, fry bacon in a skillet until crispy, then set aside on a plate. Melt butter in the same pan, add garlic, and cook until fragrant.
Add cream, salt, and pepper, and simmer for 2 minutes. Whisk in Parmesan until melted, then add spinach until wilted.
Add baked meatballs to the sauce, cooking for an additional 2 minutes. Chop the bacon and sprinkle on top.
Serve with pasta.