Peel and wash the potatoes. Several times close together cut them in half. Put into a suitable casserole dish, salt a little and pour cream over it. Cook in the preheated oven (electric cooker: 200 °C/ gas: level 3) for 20 minutes.
In the meantime, clean, wash and cut the leek into large pieces. Cut them 2-3 times deep and put them into the mould as well. Season with salt and pepper. Grate the cheese over the vegetables. Finish cooking for another 15 minutes in a preheated oven (electric cooker: 200 °C/ gas: level 3).