In a medium saucepan, bring to a boil enough water to cover chicken. Add chicken breasts and 1/2 teaspoon salt and simmer for 10 to 12 minutes or until tender.

Remove pan from heat and cool chicken in liquid. Drain chicken and cut into 1/2 inch slices. Set aside.

Cook pancetta or bacon in a large skillet over medium heat until crisp and slightly brown. Drain on paper towels. Crumble and set aside. Discard all but 2 tablespoons drippings.

Add leeks to drippings and saute over medium heat, stirring occasionally, until soft but not brown, about 5 to 7 minutes.

Add spaghetti sauce, cream, thyme, red pepper and 1/2 teaspoon salt. Bring to a boil, then reduce heat and simmer 3 to 5 minutes.

Just before serving, add pancetta and sliced chicken to sauce and heat briefly.

Pour sauce over pasta & toss. Garnish with Parmesan.