Steam or boil the potato in salted water, leave to cool and grate.
In a bowl, use a fork to mash the cheese and add the grated potato, Parmesan cheese and milk. Season with salt and mix all the ingredients together well. Add the egg and the yolks and whisk moderately.
Transfer the mixture into the darioles (greased twice) and cook in a pre-heated oven at 160°C for approximately 10 minutes.
Leave the flans to cool down on a special rack, turn out onto the serving plate and serve warm.