Start by seasoning the chicken breasts with salt, black pepper, garlic powder, and Italian seasoning on all sides. Place the seasoned chicken in the bottom of your slow cooker in a single layer. Scatter the diced onion, minced garlic, and chopped sun-dried tomatoes over the top of the chicken. Pour the chicken broth over everything, then add the cubed cream cheese around the chicken pieces.
2 pounds boneless, 1 teaspoon salt, ½ teaspoon black pepper, 1 teaspoon garlic powder, 1 teaspoon Italian seasoning, 1 small onion, 3 cloves garlic, ½ cup sun-dried tomatoes, 1 cup chicken broth, 1 block cream cheese, softened and cubed
Cover the slow cooker and cook on Low for 4 to 6 hours or on High for 2 to 3 hours, until the chicken is tender and cooked through. The chicken should reach an internal temperature of 165°F. Remove the chicken from the slow cooker and set it aside. If you prefer, you can shred or slice the chicken at this point. Whisk the cream cheese into the broth mixture in the slow cooker until it's completely smooth and no lumps remain.
Stir in the heavy cream and grated Parmesan cheese, whisking until well combined. Mix the cornstarch with cold water in a small bowl to create a slurry, then stir it into the sauce. Add the fresh spinach and increase the heat to High for 10 to 15 minutes until the sauce has thickened and the spinach is wilted.
1 cup heavy cream, ½ cup Parmesan cheese, 1 tablespoon cornstarch, 1 tablespoon cold water, 2 cups fresh spinach
Return the chicken to the slow cooker, spooning the creamy sauce over the top. Garnish with fresh basil or parsley before serving.
Fresh basil or parsley
Notes
Slice chicken for better sauce coverage - After cooking, slice the chicken breasts into medallions so each piece gets coated in the creamy sauce when served.
Use oil-packed sun-dried tomatoes - Sun-dried tomatoes packed in oil add extra richness to the dish compared to the dry-packed variety.
Don't add spinach too early - Wait until the last 10 to 15 minutes to add the spinach so it doesn't overcook and become mushy.
Adjust thickness - If your sauce is too thick, add a splash of chicken broth or milk. If it's too thin, let it cook on High uncovered for a few extra minutes.
Fresh Parmesan is best - Use freshly grated Parmesan cheese rather than pre-grated for better melting and richer flavor.