Wash the potatoes and cook for about 20 minutes. Grate both cheeses. Rinse and peel the potatoes. Press them hot through a potato press and let them cool down. Then knead with egg yolk, n-potato flour, semolina, 1 level tsp salt and 50 g Parmesan cheese.
Possibly knead in a little more potato flour.
Dust with flour to make the gnocchi work surface. Prepare the potato mixture on it step by step with floured hands. Let the gnocchi rest for about 15 minutes.
For the sauce, heat the fat. Sweat 3 tbsp. flour in it. Stir in cream, a good 1/2 l water and stock, bring to the boil. Simmer for about 5 minutes. Put 2 tbsp. of the parmesan aside. Melt the rest and provolone in the sauce.
Clean, wash and coarsely chop the arugula. Roast the seeds until golden brown. Cook gnocchi in portions in plenty of boiling salted water for 4-6 minutes (do not boil!) until they float to the surface.
Lift out, drain well. Stir the arugula into the cheese sauce. Serve everything. Sprinkle with seeds and the rest of the cheese.