Season the chicken thighs with half of the ranch seasoning, smoked paprika, and black pepper.
Heat a large skillet over medium heat and melt the 2 tablespoons of butter. Sear the chicken thighs on both sides until brown, about 3 minutes per side.
Transfer the seared chicken to the slow cooker. Add the minced garlic, chopped onion, and chicken broth. Cook on low for 5-6 hours or high for 3-4 hours until the chicken is tender and cooked through.
In the last 30 minutes of cooking, stir in the Greek yogurt, remaining ranch seasoning and dried dill. Allow the sauce to combine with the chicken, creating a creamy, flavorful gravy. You can adjust the amount of yogurt for a creamier sauce.
In the last 45 minutes of the chicken cooking, bring a large, salted pot of water to a boil. Peel and chop the potatoes into even sized cubes.
Add the cubed potatoes and whole garlic cloves into the pot. Cook until the potatoes are tender, about 15-20 minutes.
Drain the potatoes and garlic, then return them to the pot. Add the butter, heavy cream, and Parmesan cheese. Mash until smooth and creamy. Add in salt and pepper to your preferred taste. Cover the pot and keep warm until ready to serve.
Plate the mashed potatoes and spoon the ranch chicken with its creamy sauce over the top. Garnish with freshly chopped chives for a pop of color and extra flavor.