Bring a pot of salted water to a boil and cook tortellini as directed to al dente; during the last 2-3 minutes of cooking, add the peas to the boiling water. Drain pasta and reserve 1/2 cup of pasta water.
While the tortellini is cooking, melt butter in a large pan over medium heat. Add the diced pancetta to the pan and stir until it begins to crisp.
Add the leeks and garlic to the pan, and sauté until the leeks have softened.
Deglaze the pan with white wine, and use a wooden spoon to scrape up any bits from the bottom of the pan. Stir in the reserved pasta water and simmer until the sauce reduces slightly.
Add the tortellini, peas, and parmesan cheese to the sauce in the pan and toss to coat.
Season with fresh black pepper and drizzle with olive oil and fresh parsley before serving.