01 - Pat chicken breasts dry and season both sides evenly with salt, freshly ground black pepper, paprika, and dried Italian herbs.
02 - Spread the chopped onion, minced garlic, and sliced sun-dried tomatoes across the bottom of the slow cooker insert.
03 - Arrange the seasoned chicken breasts in a single layer on top of the vegetable base.
04 - Pour the chicken broth and heavy cream evenly over the chicken. Dot the surface with small pieces of unsalted butter.
05 - Cover the slow cooker and cook on the low setting for 4 to 6 hours, or until the chicken is tender and reaches an internal temperature of 165°F.
06 - About 20 minutes before serving, add the packed baby spinach and grated Parmesan cheese. Stir gently to wilt the spinach and incorporate the cheese into the sauce until smooth.
07 - Taste the creamy sauce and adjust salt and pepper as desired.
08 - Plate the chicken breasts and spoon the creamy Tuscan sauce generously over the top. Serve immediately.