Maybe it is a stretch to call this "skinny" but it is certainly lower in fat than my regular mac and cheese. My favorite is still Pioneer Woman's, but if you are trying to diet, then this one is pretty good. It came in at 178 calories for a 12th of the pan with 4 grams of fat, 12 grams of protein, 27 grams of carbs and 2.5 grams of fiber.
12 oz. of Ronzoni smart taste pasta (tastes like white but has nutrition of wheat)
12 oz. can of evaporated non-fat milk
8 oz. of 2% shredded cheddar cheese (reserve 1/4 c.)
1/2 c. non-fat sour cream
1 t. dried mustard powder
1/2 t. salt and 1/2 t. pepper
Cook the macaroni and drain. Add the milk to a saucepan. When it just starts to bubble around the edges, remove from heat and whisk in the cheese, sour cream, mustard, salt and pepper until smooth. Stir in the macaroni. Pour into a 9 x 13 pan sprayed with Pam. Sprinkle with the reserved cheese. Cover with aluminum foil. Bake 20 minutes. Remove the foil and bake 10 more.