Sear the Meat: Optionally, sear the ribeye chunks and chicken in a skillet over medium-high heat for 2-3 minutes on each side to lock in flavor.
Prepare the Slow Cooker: Place the seared ribeye and chicken in the slow cooker.
Season: Sprinkle the ranch and au jus seasoning packets over the meat. Add the pepperoncini peppers and juice, then top everything with slices of butter and minced garlic.
Slow Cook: Cover and cook on low for 5-6 hours or on high for 3-4 hours, until the meat is tender and full of flavor.
Make the Sauce: In the last 30 minutes, add heavy cream and Parmesan to the slow cooker. Stir gently to create a creamy garlic Parmesan sauce that coats the chicken and steak.
Prepare the Mashed Potatoes: While the slow cooker finishes, boil the diced potatoes in salted water until tender, about 15 minutes. Drain and mash with butter, cream, and Parmesan cheese. Season with salt and pepper to taste.
Serve: Spoon the garlic butter chicken and ribeye over a bed of Parmesan mashed potatoes. Garnish with fresh parsley.
