Holding an asparagus spear in both hands, bend the spear until it breaks naturally at the point where the spear becomes tough. Discard the tough end and repeat with the remaining asparagus. Cut the asparagus into 1-inch lengths. Bring a large pot of salted water to a boil. While the water heats, cook the olive oil and pancetta in a skillet over moderately low heat until the pancetta is almost crisp, about 5 minutes. Add the leek and sauté until softened but not colored. Add the asparagus to the boiling water and cook until just tender, 3 to 4 minutes. Drain and add to the skillet. Season with salt and pepper and toss to coat with the seasonings. Transfer to a serving bowl and serve immediately. |