Place prepared potatoes into Varoma dish and tray and water into Thermomix bowl. Steam 25 min/Varoma/speed 3.
Remove potatoes and cool slightly. Drain water from bowl.
Place onion, butter, wine and salt into Thermomix bowl. Chop 4 sec/speed 5. Saute 8 min/Varoma/speed 1.
Meanwhile preheat your oven to as hot as you can get it. Around 220ºC if possible. (Not a grill, an oven function.)
Butter a large pie dish, casserole dish or several individual ramekin dishes.
Now, for the hard part….Lay potatoes, lardons, sauteed onions, in prepared dish. Cut the cheese into pieces and dot the surface of everything else. Bake until golden and fragrant…about 20-25 minutes.
If you had a whole rinded cheese (Reblochon is authentic) and your dish was the right size, you could just put the whole cheese on top and bake it as is…can you imagine?? (I can…and so I restricted myself to less cheese…and the dot method…to preserve my hips for another day!)