Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper and lightly grease with oil or cooking spray.
Mix meatballs: In a large bowl, combine ground chicken, ricotta, Parmesan, breadcrumbs, egg, garlic, onion powder, Italian seasoning, salt, and pepper. Mix until just combined—don’t overwork the mixture.
Use a small scoop or your hands to form 1.5-inch meatballs and place them evenly spaced on the prepared sheet.
Bake for 18–20 minutes, or until golden and cooked through (internal temp 165°F).
While baking, make the sauce: In a large skillet, melt butter over medium heat. Add garlic and sauté for 1 minute.
Stir in flour and cook for 1 more minute, whisking constantly.
Slowly whisk in milk and cream until smooth. Bring to a gentle simmer and cook until thickened, about 3–5 minutes.
Stir in Parmesan cheese, salt, pepper, and a pinch of nutmeg (if using). Add chopped spinach and cook until wilted.
Add baked meatballs into the sauce, gently coating them. Simmer for 2–3 minutes to let flavors meld.
Serve over pasta or rice, or enjoy them on their own with crusty bread. Garnish with herbs and extra Parmesan.