Heat the milk in a trustworthy pan until warm then add the semolina. Pour it in slowly, steadily stirring all the time (it’s best for two people, if possible, to do this -one to pour, one to stir). Continue to stir over a medium heat for 15–20 minutes until the semolina forms a mass coming away from the side of the pan.
Allow this mixture to cool a little, then add the Parmesan, egg yolks and butter. Mix very well. Lightly oil a Swiss roll tin or roasting dish and pour the mixture into it. It should not be deeper than 2 cm. Allow to cool completely, then clingfilm and refrigerate overnight.
An hour before serving,
Butter the ovenproof dish. Cut the semolina into 4 cm circles and arrange them overlapping like roof tiles around the circumference of the dish. Start another oval within this and continue until you have either filled the dish or run out of semolina to cut. If you have run out before the dish is full, use the off cuts from between the circles to fill the gaps. The gnocchi discs should overlap so much they are standing nearly vertically. Dot the completed dish with butter and scatter the Parmesan over.
Serve directly from the dish, still very hot. Serve your guests yourself, otherwise they will inevitably burn themselves on the hot dish.