{Healthier} Homemade Mac 'n' Cheese

12 ounces large, whole wheat elbow macaroni
2 cups (8 ounces) shredded sharp cheddar cheese
1 egg or 1/4 cup egg substitute
1 1/2 teaspoons kosher salt
1 (12-ounce) can evaporated low-fat milk
1/2 cup pureed squash (any yellow variety) or pureed cauliflower

Cook macaroni per package instructions. Return drained pasta to the pot and add remaining ingredients. Cook for about 4-5 minutes over medium heat, stirring constantly, until the cheese is melted.