1: Prepare one potato per person: hollow out the centre using a pommes parisiennes spoon or a teaspoon to create the "nest". Trim off the ends if necessary to tidy the shape.
2: Slice the rest of the potatoes.
3: Pan-fry the potato slices on both sides in a little olive oil, then salt and set aside and keep hot.
4: Fry the potato nests until browned all over. Heat 250 g cancoillotte in the microwave or in a bain-marie.
5: Heat the plates. Stand a nest in the centre of each hot plate and surround with the fried potato slices. Slip an egg yolk into each nest and salt lightly.
6: Fill up the nests with hot cancoillote and pour a little over the potatoes. Serve immediately.
Remarks
If you don't have any cancoillote, use any other cheese you like (but preferably a soft cheese) and melt it in a little cream. You may be surprised to see that the egg yolk is not heated beforehand, but it will heat through when in contact with the hot potato and cheese.