To roast the peppers, place them on a baking sheet lined with aluminum foil about 8 inches from the broiler. Broil them until the skin blisters and turns black on both sides (do not burn the chilies themselves - only the skin). Turn once during broiling. Remove the baking sheet from the oven and quickly cover the peppers with a clean dish towel. Let them sit, covered, until they are cool. Using a paring knife or your fingers, carefully peel off the skins, then slit one side and remove the seeds and veins. Cut the peppers into thin strips.
Melt the butter in the bottom of the slow cooker insert. Place a layer of sliced potatoes in the bottom of the slow cooker insert (the author states that she uses a bit more than one potato per layer). Sprinkle lightly with freshly ground smoked or regular salt. Place a thin layer of cheese (about 1/3 of the cheese) on top of the potatoes. Place about half of the pepper strips on top of the cheese. Repeat with another layer of potatoes, salt, cheese and peppers. Finish with a layer of potatoes.
Pour the water over the potatoes. Cover and cook on low for about 1 1/2 hours, or until the potatoes are beginning to get tender.
Using a garlic press, press the garlic into the cream; pour the cream mixture over the potatoes, then add a last layer of the cheese sprinkled with a bit of salt. Re-cover and cook for another 3 hours or until the sauce has thickened and the potatoes are quite tender.