*If using ground nutmeg rather than grating it fresh, first mix it in with the heavy cream for even distribution.
Preheat the oven to 350 degrees. Slice the potatoes as thin as possible, about 1/8 inch or less, using a mandolin slicer or a sharp knife.
Rub the bottom and sides of an 8×8 (or similar sized) baking dish with softened Finlandia butter, then place a single layer of potatoes on the bottom. Sprinkle lightly with salt and pepper, and then with scant layer of grated Finlandia Swiss cheese. Repeat with layers of potato, salt, pep-per and cheese until you’ve used everything up.
Pour heavy cream over the potatoes, then use your fingers to gently press out any air pockets. Freshly grate nutmeg* over top, then cover with panko breadcrumbs.
Bake for about one hour (possibly longer), or until the top is golden brown and a knife can be easily inserted in the center, indicating that no raw pieces of potato remain. If the potatoes are still underdone and the top is getting too brown, cover with foil for the remainder of cooking time.
Allow the gratin to cool down for at least 10 minutes before cutting. Garnish with chopped fresh chives if desired.