With the rack in the middle position, preheat the oven to 180 °C (350 °F).
Wash the potatoes and sweet potatoes, drain and slice them thinly with a mandolin. Do not rinse the sliced potatoes so that they retain maximum starch.
Butter the sides and bottom of a 30 x 20-cm (12 x 8-inch) baking dish. Line the bottom of the dish with slices of sweet potatoes. Sprinkle with cheese and drizzle with cream. Season with salt and pepper. Cover with a layer of potatoes, drizzle with cream and sprinkle with chives. Continue with all the ingredients and season with salt and pepper between each layer. Cover with aluminum foil.
Bake for about 1 hour or until the vegetables are tender.
If necessary, brown under the broiler. Let stand for 10 minutes, cut into squares and serve.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.