Cook the whole, unpeeled potatoes in a pot of unsalted water to cover at a steady boil for 20 minutes or longer until just cooked through. Don't let them crack or get mushy on the outside. Let them cool briefly, then peel and slice them into rounds, 1/4-inch thick.
Heat the oil and the bacon pieces in a skillet over medium heat, stirring occasionally, for 3 or 4 minutes until the bacon is sizzling and has rendered much of its fat. Stir in the leeks and cook another 3 minutes or so until they're wilted and sizzling. Spread the potato slices in the pan, season with salt and pepper and toss with the bacon and leeks.
Cook for 8 minutes or more over medium-high heat, breaking up the potatoes into chunks. Spread and press the filling flat in the pan and let caramelize for a couple of minutes. Turn the pieces, press and fry, then repeat. When the filling is thoroughly cooked and has started to color, scrape it into a mixing bowl. Cool briefly then crush the potatoes some more with a fork (I like to have little chunks left); add 1/2 cup Parmesan and salt and pepper, to taste.
Roll out fresh pasta dough. For each ravioli, scoop up a heaping tablespoon of potato filling, shape it round and set in place. Cover and cut ravioli.
Bring a large pot of salted water to boil. If you are using dry pasta, start cooking the pasta 5 minutes before you start the sauce; if you are using fresh, start the sauce and then put on the pasta to cook at the same time
When the pasta is done al dente, scoop it up and drop into the shrimp pan. Toss briefly, sprinkle on the parsley, and toss again. Remove from the heat and drop 2 tablespoons butter on top of the pasta and toss in. Serve right away sprinkled with Parmesan.
Hot water from the pasta cooking pot
Pour the olive oil into the big skillet, scatter the garlic slices in and set over medium-high heat. Cook for 1 minute, until the garlic is sizzling. Scatter the slices of pepperoncini in a hot spot; cook for 1 minute; shake the pan now and then. Push the garlic and peppers to the side, turn the heat to high. Drop the shrimp in the center of the skillet and spread them so they're not crowded. Sprinkle on the salt and let them sizzle for 1/2 minute. Flip the shrimp over, giving the skillet a good toss or stirring and turning them; and cook another 1/2 minute or so, until the flesh is just turning opaque. Scatter the scallions into the skillet; toss and stir in with the shrimp, for 20 to 30 seconds, just until they are sizzling. Stir in butter 2 tablespoons of butter and cook until it is melted and starts to simmer, 10 to 20 seconds. Ladle in 2 cups of boiling pasta water. Stir up everything in the skillet and let the sauce boil for only a moment. If the pasta is ready to add turn down the heat to very low. If the pasta is not ready, remove the skillet from the heat immediately; set it back over low heat when you do add the pasta.
Yield: sauce for 1 pound pasta