Spray slow cooker with cooking spray.

Season chicken breasts with salt and pepper. Heat oil in a large skillet over medium-high heat. Sear chicken breasts on both sides until golden brown. Arrange the chicken in single layer in bottom of slow cooker.

Add garlic cloves to the same skillet, and cook until just golden. Carefully add 1/2 cup of broth to the skillet and scrape up any browned bits from bottom. Simmer for 1 minute.

Pour the garlic mixture into the slow cooker. Add the remaining broth and stir gently to combine. Add thyme sprigs. Cover and cook on high for 4 hours.

Twenty minutes before serving, whisk together the cornstarch and water. Remove the chicken from the slow cooker to a plate. Stir the cornstarch mixture, Parmesan cheese and whipping cream into the liquid in slow cooker.

Return the chicken to the slow cooker. Cover and cook 20-30 minutes longer, or until sauce is thickened.

Serve over cooked pasta and garnish with parsley and additional Parmesan cheese.