Wash potatoes and place each on a piece of aluminum foil. Sprinkle with salt and wrap in foil. Bake in the preheated oven at 200 °C for about 35 minutes. Remove, unwrap and allow to steam briefly.
Cut a lid off the length of 4 (!) potatoes and carefully scoop out the potatoes with a small spoon. Strain the leftover potatoes. Cut the fifth potato into small cubes.
Peel peppers, remove stem and seeds and cut into small cubes. Dip tomato briefly in boiling water, peel and also cut into small cubes.
Mix tomato and bell pepper cubes with potato mixture and cubes. Season with salt, pepper and nutmeg.
Stir in egg yolks. Beat egg whites until stiff and fold in.
Fill the mixture into the hollowed potatoes and sprinkle with grated cheese. Bake in the preheated oven at 200 °C for 8-10 minutes.
Remove, arrange on plates and garnish with chopped chives.