Wash the potatoes, dry them and wrap them in foil. Grate the cheese on a coarse grater.
Preheat the oven to 200°C, bake the potatoes for 40 minutes. Fry the spinach in oil, without defrosting, for 3 minutes. Add some salt. Cut the baked potatoes in half lengthwise.
Remove the pulp from the potatoes with a spoon. Mix it with spinach and cheese. Stir and fill potato boats. Bake for another 5 minutes.
Serve potato boats with vegetables, sour cream or sauce.