With a fork, make a few vent holes in the potatoes to allow the steam to escape. Bake in a 400 degree oven until tender, 45 minutes. While potatoes are still warm, peel and pass through a food mill or ricer. While still warm, mix in flour, egg, butter, parmesan cheese, and a pinch of salt until dough is formed. Roll the mixture into 2 rolls about 1 inch thick on a lightly floured surface; cut them into ¾ inch pieces. Roll the back of a fork across each piece. Place the pieces on cheesecloth, dusted with flour. To make sauce, melt asiago, and parmesan cheese together with cream. Heat olive oil and sauté leeks until translucent; add to cheese sauce. When ready to serve, place gnocchi in boiling salted water; cook until they rise to the surface. Drain well and serve with the sauce; grate additional cheese on top if desired.