1. Heat the olive oil in a skillet over medium-high heat. Season the chicken breasts with salt and pepper, then sear them in the skillet for 2-3 minutes on each side until golden brown. Transfer the chicken to your slow cooker.
2. In the same skillet, add the onions and cook until they become translucent. Add the garlic, mushrooms, and sun-dried tomatoes, cooking for another 2-3 minutes until everything is well combined.
3. Pour the Marsala wine into the skillet, scraping up any browned bits from the bottom. Let it simmer for 2 minutes, then add the chicken broth. Transfer this mixture to the slow cooker.
4. Add the oregano, basil, and a bit more salt and pepper to the slow cooker, then give everything a gentle stir. Cover and cook on low for 6-7 hours or on high for 3-4 hours.
5. About 30 minutes before serving, mix the cornstarch with water to create a slurry. Stir this into the slow cooker, along with the heavy cream. Allow it to cook for an additional 30 minutes to thicken the sauce.
6. Once done, serve the chicken with your choice of side dishes, making sure to drizzle plenty of the Marsala sauce over the top. Enjoy!
