In a large bowl, whisk together heavy cream (or half and half), chicken broth, paprika, nutmeg, thyme, rosemary, and garlic powder until combined.
Line bottom of a slow-cooker with a layer of potatoes, then top with ⅓ of cream mixture, ½ cup parmesan and ½ cup gruyère. Season with salt and pepper. Repeat until all ingredients are used up. Cover and cook on high for 4 hours.
Remove the lid, turn off heat, and let set 30 minutes. (Drain any grease.) Transfer to a bowl and garnish with more thyme and rosemary, then serve.
