Prepare the Chicken: Season the chicken breasts with salt and pepper. Heat the olive oil in a skillet over medium-high heat. Once hot, sear the chicken breasts for 2-3 minutes per side until they are lightly golden brown. This step helps lock in moisture and adds extra flavor to the chicken.

Add Ingredients to Slow Cooker: In your slow cooker, add the diced tomatoes, tomato paste, heavy cream, chicken broth, garlic, Parmesan cheese, dried basil, onion powder, and crushed red pepper flakes (if using). Stir to combine the ingredients until the sauce is smooth.

Add the Chicken: Place the seared chicken breasts into the slow cooker, making sure they are covered with the sauce. The chicken doesn’t need to be submerged, but it should be well-coated with the tomato mixture.

Cook the Chicken: Cover the slow cooker and cook on low for 4-6 hours, or until the chicken is tender and fully cooked. The internal temperature of the chicken should reach 165°F (75°C). If you want the sauce to thicken further, you can remove the chicken about 30 minutes before serving and cook the sauce on high for a thicker consistency.

Shred the Chicken (Optional): For a more rustic texture, shred the chicken in the slow cooker using two forks. This will allow the chicken to absorb more of the flavorful sauce. Alternatively, you can serve the chicken breasts whole.

Serve: Garnish with fresh basil leaves and additional Parmesan cheese before serving. Serve the chicken over pasta, rice, mashed potatoes, or a bed of greens for a complete meal.