Soften the potatoes in their skins, not too soft.
Cut the peppers in half, remove the seeds and cut into strips. Cook in not too much salted water for four minutes. Drain well.
Cut half of the cheese into slices and spread them on the bottom of a very generously buttered baking dish. Remove the peel from the still hot potatoes, cut them into thick slices, layer them like a brick on top of the cheese and season sparingly with salt and enough pepper. Cut the remaining cheese into slices and spread evenly over the potatoes. Add the pepper strips on top. Drizzle everything with white wine, sprinkle with a little cumin and paprika to taste.
Bake the gratin on the spot in the oven heated to 220 degrees on the second rack from the bottom for about 20 minutes. Bring to the table very hot.