Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish.

Pat the chicken dry and season both sides with salt and pepper. If using chicken breasts, slice them in half horizontally so they cook evenly.

Warm olive oil in a large skillet over medium-high heat. Sear the chicken 2–3 minutes per side until lightly browned. It won’t be fully cooked yet—just golden. Transfer to the baking dish in a single layer.

Lower the heat to medium. In the same skillet, add garlic and cook 30 seconds until fragrant. Stir in the cream cheese, heavy cream, and chicken broth. Whisk until smooth and creamy.

Stir in Parmesan, Italian seasoning, and red pepper flakes if using. Fold in the sun-dried tomatoes and spinach until the greens just wilt.

Pour the sauce evenly over the chicken. Top with shredded mozzarella.

Bake uncovered for 22–28 minutes, or until the chicken reaches 165°F (74°C) in the thickest part and the top is bubbly.

Broil for 1–2 minutes if you want extra color on the cheese. Rest 5 minutes, then garnish with fresh basil or parsley.

Serve with zucchini noodles, roasted broccoli, sautéed green beans, or a simple side salad.