Season the chicken breasts with salt, pepper, garlic powder, onion powder, and Italian herbs on both sides.
In a large skillet, heat the olive oil over medium-high heat. Add the seasoned chicken breasts and sear for 3-4 minutes on each side until golden brown. Remove from heat.
In a slow cooker, combine the sun-dried tomatoes, heavy cream, and Parmesan cheese. Stir until well mixed.
Place the seared chicken breasts on top of the cream mixture in the slow cooker. Cover and cook on low for 4-6 hours or on high for 2-3 hours, until the chicken is cooked through and tender.
About 15 minutes before serving, stir in the chopped spinach and let it wilt in the sauce.
Serve the chicken with the creamy sauce over pasta, rice, or with crusty bread. Garnish with fresh basil leaves if desired.