COOK pancetta, onion and rosemary in a large skillet over medium-high heat, stirring frequently, for 2 to 3 minutes or until pancetta is cooked. Stir in potato and water. Reduce heat to medium; cook for 5 to 8 minutes or until potato is tender. Season with ground black pepper.
MASH the potatoes with a fork to obtain a creamy sauce. If too thick, add about ¼ cup more water and continue to mash. Cover until pasta is ready.
PREPARE pasta according to package directions. Drain. Add to skillet; toss gently to coat. Garnish with additional fresh rosemary, if desired.