Ok, so I am something of a mac & cheese fiend and am always up for making this at home. Fortunately, my BF is more health conscious than I am so we are trying to find a recipe that is more low-fat than your typical recipe. We made the recipe from Cooks Illustrated a few months ago and it was delicious. It was NOT low-fat. The new issue of Cooking Light has a recipe that has ham and peas in it and we thought we would try it out. It called for skim milk and reduced fat cheddar and swiss. When I brought the milk mixture to a simmer, I added all the cheese, as instructed. The cheese never melted! It turned into this nasty curd-y mess. Any idea what went wrong? I trying to up the heat, I tried to beat the cheese mixture with beaters, I tried adding flour to thicken it and nothing worked. We were left with this hot milk with nasty cheese bits in it. We bailed and added tomato sauce to the already cooked elbows, pancetta and peas. Was is simply a matter of low-fat means no melting? Any recommendations on how to do it right? Anyone want to share a "low-fat" recipe for mac & cheese? Thanks!