Gnocchi Gratin

2 lbs gnocchi, cooked to package instructions 2 cups milk 4 tablespoons butter 1/4 cup all-purpose flour 1/2 teaspoon kosher salt 1/4 lb parmigiano-reggiano[...]

1 lb potato , unpeeled 1 1/2 egg yolks 3/4 cup all-purpose flour , plus additional flour , for dusting surface 1 pinch freshly grated nutmeg salt & freshly[...]