4 small ramequins (individual soufflé dishes) made of oven-proof porcelain or glass
Preheat the oven to 200°C/400°F/Mark 6. Peel and wash the smaller of the two potatoes. Remove the outer skins and roots of the leek, cut it in half and wash it carefully, separating the layers to remove all traces of grit.
Bake the larger potato, washed but not peeled, in the oven for 40 minutes. Test it with the point of a small knife to make sure that it is cooked.
Cut the leek lengthwise into julienne strips and put in a small saucepan with half a tablespoon of the butter and 2tablespoons of water. Cook over a moderate heat for 10 minutes until the water has completely evaporated. Remove from the heat and keep hot. Cut the small potato into dice and rinse under the cold tap in a colander. Leave to drain.
Warm through the milk and cream in a small saucepan and meanwhile beat the two eggs in a bowl.
When the large potato is cooked (2) lower the heat of the oven to 170°C/325°F/Mark 3. Cut the baked potato into four and scoop out the inside with a spoon. Sieve the flesh through a mouli-légumes into a large bowl and whisk in the warm milk and cream. Add the beaten eggs and whisk until all the ingredients are thoroughly mixed. Season with salt and pepper and 2–3 gratings of nutmeg. Add the cooked leek and the diced raw potato (3) and stir lightly to distribute them evenly.
Butter each ramequin, using a pastry-brush or your finger, and making sure that they are evenly coated. Ladle the mixture into the ramequins and place them in a pan of water prepared as described in the previous recipe. Cook in the oven for 25 minutes. To serve, simply turn out the potato and leek moulds on to a heated serving plate.