Prep the slow cooker. Lightly grease the crock with olive oil or spray to prevent sticking. Set aside.

Make the meatball mixture. In a large bowl, combine ground turkey, eggs, breadcrumbs, 3/4 cup Parmesan, half the minced garlic, onion, parsley, Italian seasoning, red pepper flakes (if using), 1 1/4 teaspoons salt, and 1/2 teaspoon black pepper. Mix gently with a fork or your hands until just combined. Don’t overwork.

Shape the meatballs. Use a 1 1/2-inch scoop or roll by hand to form about 28–32 meatballs. Lightly oil your hands to keep them from sticking.

Optional sear for extra flavor. Heat a large skillet with a drizzle of olive oil over medium-high. Brown meatballs in batches for 1–2 minutes per side, just until golden. They don’t need to be cooked through. This step adds flavor, but you can skip it for convenience.

Build the sauce base. Add chicken broth, butter, remaining garlic, lemon zest, and a pinch of salt and pepper to the slow cooker. Whisk in cream cheese until mostly smooth (small specks are fine).

Load the crockpot. Nestle the meatballs into the sauce base in an even layer. Spoon a little sauce over the top.

Cook low and slow. Cover and cook on Low for 3 1/2–4 1/2 hours or on High for 2–2 1/2 hours, until the meatballs reach an internal temperature of 165°F (74°C).

Finish the sauce. Stir in heavy cream, 1/4 cup Parmesan, and lemon juice. If you’re adding spinach, toss it in now. Cover and cook on High for 10–15 more minutes, until the sauce is silky and the spinach wilts.

Taste and adjust. Add salt, pepper, or a pinch of red pepper flakes to taste. For a thicker sauce, uncover and cook 10 more minutes.

Serve. Sprinkle with extra Parmesan and chopped parsley. Serve over pasta, rice, mashed potatoes, or with crusty bread.