1: Preheat the oven to 430°F (220°C). Cut 1 kg cooked potatoeses in half lengthways.
2: Arrange them cut face downwards on a sheet of baking parchment laid on a baking sheet. Brush with olive oil, then sprinkle with a little salt.
3: Turn the potatoes over and spread with a generous helping of bechamel sauce.
4: Lay a slice of ham on each one.
5: Finish with a little grated cheese.
6: Bake for about 20 minutes until nicely browned on top.
Remarks
If your potatoes are quite large, carve a hollow with a pommes parisiennes spoon to make room for a little more bechamel sauce, otherwise they might be too dry.