Put a large saucepan of lightly salted water on to boil. Add the leeks and cook gently for 3 minutes until just tender. Remove the leeks to a plate using a slotted spoon. Preheat the grill to medium.
Place the pancetta on the rack of the grill tray and grill for 2 minutes until beginning to become crisp. Remove and break into rough pieces.
Bring the water back to the boil and if necessary, top up with a little more boiling water from the kettle. Drop the pasta into the water and cook for 6 minutes, or according to the packet instructions. Add the peas to the water for the last 3 minutes of the cooking time and bring back to the boil. Stir occasionally to make sure that no pasta is sticking to the base of the pan.
Lightly whisk the eggs with the sour cream and freshly ground black pepper to season. Drain the pasta and peas and immediately return them to the hot pan. Stir in the egg mixture, which will cook in the heat of the pasta. Then quickly add the pancetta, leeks and parsley and lightly toss everything together.
Sprinkle the parmesan over the top and season to taste with more pepper. Serve immediately.