Wrap each potato individually in aluminum foil and bake them on a bed of coarse salt at 200°C (392°F) for about 1 hour. While still hot, mash them using a potato ricer. In a bowl, mix the mashed potatoes evenly with melted butter, Aged Pecorino Sardo DOP, flour, and egg yolk. Season with salt, pepper, and nutmeg. Let the dough rest for 15 minutes. In a small saucepan, melt the chopped Moliterno Vignaiolo Pecorino with the fresh cream until you get a smooth textured, glossy violet-colored sauce. Using flour to help with shaping, form the gnocchi into uniform balls. First boil them in salted water for a few minutes, then lightly sear them in a pan with a drizzle of extra virgin olive oil. Slice the remaining Moliterno Vignaiolo Pecorino thinly and cut into 5 cm disks; set them aside. Serve the gnocchi hot, accompanied by the creamy sauce and cheese disks. Garnish with wild fennel for an aromatic touch.