9: Put 2/3 of the grated Comté into a bowl, add 250 ml liquid cream and mix well.
10:
Assembling the gratin
Preheat the oven to 390°F (200°C). Butter a gratin dish and spread half the potatoes in an even layer.
11: Add the diced mustard-flavoured ham...
12: ...then the rest of the potatoes...
13: ...and pour the gratin sauce over.
14: Finish by scattering the remaining Comté on top.
15: Bake for about 30 minutes.
Remarks
You can use a bouquet garni or a bayleaf instead of the sprig of rosemary in stage 2. For the ham, the ideal thing is to buy an end of ham from your butcher or deli. If not, ask for a slice about half an inch thick.