Prep the chicken: Pat the chicken dry and season both sides with salt and pepper. If using large breasts, you can cut them in half horizontally for quicker, more even cooking.
Make the sauce base: In a bowl, mix cream cheese, heavy cream, mayonnaise, Parmesan, garlic, onion powder, Italian seasoning, red pepper flakes, and a pinch of salt and pepper.
Stir until smooth.
Layer the slow cooker: Lightly grease the crockpot. Add the chicken in an even layer. Spread the cream cheese mixture over the top, coating the chicken well.
Add the veggies: Scatter chopped artichokes and spinach over the sauce.
If using frozen spinach, make sure it’s thoroughly squeezed dry to avoid a watery sauce.
Cook low and slow: Cover and cook on Low for 3.5–4.5 hours, or on High for 2–3 hours. Chicken is done when it reaches 165°F and shreds or cuts easily.
Finish with mozzarella: About 10–15 minutes before serving, sprinkle mozzarella on top. Cover and let it melt into the sauce.
Adjust and brighten: Stir everything together.
Taste and add more salt, pepper, or a squeeze of lemon juice/zest if you like a little brightness to cut the richness.
Serve: Spoon over cauliflower rice, zucchini noodles, spaghetti squash, or simply plate with roasted broccoli or a side salad.