In a large pot or dutch oven, bring salted water to a boil. Cook macaroni according to package directions. Drain and set aside.
Meanwhile, in a medium saucepan melt butter over medium low heat, stirring frequently. Stir in flour until mixed in and thickens. Slowly add milk, whisking continuously while doing so. Break up any clumps that form and work them into the sauce.
Once sauce is smooth, add cheddar cheese and pumpkin to milk and butter mixture. Increase heat to medium and continue using whisk until cheese is melted completely.
Pour cheese sauce over pasta and mix until pasta is evenly coated with cheese.
Serve with a sprinkle of whole wheat bread crumbs and parmesan cheese on top.