Cook bacon in a skillet coated with Teflon™ nonstick; drain keeping 1 tablespoon fat in pan; dice & set aside. Add fresh squash to the pan & cook on medium 10 minutes; add leeks; cook 8 minutes more (less time if using frozen squash). Cook pasta as directed. Meanwhile, melt butter bubbly over medium heat in a saucepan coated with Teflon™ nonstick. Add flour, stirring 3 minutes; slowly whisk in milk and cook 5 minutes to thicken slightly. Fold in cheeses. Drain pasta and coat with cheese sauce. Turn in squash; transfer to serving dish and top with bacon.