Place potatoes on a sheet tray and cook until easily pierced with a fork, about 60 minutes. Remove potatoes from oven, let cool until easy to handle. Peel potatoes and let cool.
Line a sheet tray with parchment paper. Place prosciutto on parchment. Bake until crispy, about 8 to 10 minutes. Set aside.
Grate potatoes until fine. Make a well in the center of the potatoes, add egg, Parmesan and ricotta cheese. Whisk egg and cheese together until blended. Using your hands, gently mix with the potatoes. Add flour 1/2 cup at a time while folding together. Do not over work, this makes the dough heavy.
Dust work surface with flour. Form dough into a 1-inch-thick round. Cut into 1-inch strips. Roll each piece into a log. Cut into 1-inch pieces. Using the back of a fork, slightly press gnocchi and roll down to make ridges. At this point you could freeze the gnocchi if you want to.
Bring a large pot of water to a boil. Add a generous amount of salt. Cooking in batches, drop gnocchi into water and cook for 1 minute; gnocchi should rise to the surface when done.
In a large skillet on medium-high heat, add butter. Saute shallots until tender, about 3 minutes. Turn down heat, add heavy cream, simmer for 1 to 2 minutes until slightly thickened. Stir in peas and Parmesan, simmer for 1 minute. If sauce is too thick, add 1/4 cup of pasta water at a time. Add gnocchi and toss. Salt and pepper to taste. Divide between 4 plates. Top with crumbled crispy prosciutto.