Prep. Lightly grease a 6-quart slow cooker with cooking spray and set aside.

Prepare the chicken. Season chicken breasts all around with garlic powder, dried basil, thyme, paprika, salt, and pepper.

Sear the chicken breasts. Heat the olive oil in a skillet over medium-high heat. Add the seasoned chicken breasts to the hot oil and cook for 3 minutes per side or until just browned. Transfer the chicken to the slow cooker and top with mushrooms and garlic.

Add the wine. Return the skillet to medium-high heat and add the marsala wine; cook for 1 minute, scraping up all the browned bits from the bottom of the skillet. Pour the wine over the chicken and mushrooms.

Cook. Close with a lid and cook on LOW for 4 to 5 hours or on HIGH for 2 to 3 hours. The chicken is done when its internal temperature reaches 165˚F. Remove the chicken breasts from the slow cooker and set aside on a plate.

Thicken the sauce. Combine the water and cornstarch in a mug or a small mixing bowl and whisk until incorporated; then, whisk the slurry into the wine sauce. Add heavy cream to the wine sauce and whisk until combined. Taste for salt and pepper, and adjust accordingly.

Continue to cook. Return the chicken to the slow cooker, cover with the lid, and cook on HIGH for 20 more minutes or until the sauce has thickened. You can add more heavy cream for a creamier texture.

Serve. Transfer the chicken to dinner plates, top with the creamy mushroom sauce, garnish with fresh parsley, and serve.