Peel and cut the potatoes in 1/2 cm thick slices. Boil the potatoes in lightly salted water.

Cut the white muscle out of the shells, halve each muscle, and fry in a red-hot pan for 30 seconds on each side.

Rinse the spinach leaves and fry them quickly in hot oil. Peel and clean the lemon. Remove the stones and membranes, then fillet.

Sauce: Melt the butter at low temperature. Whisk the egg yolks and lemon juice in a water bath. Dilute carefully with the melted butter while stirring.