My elderly aunt taught me a lesson on making low fat mashed potatoes. After draining them, and using just a tiny dab of lowfat margarine, I start whipping them and adding, just a little at a time, fat free non dairy creamer.
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I discovered a great way for making mashed potatoes, and I don't use any fat in it. While making the potatoes for mashing, I put a can of vegetable broth into a pan, and just simmered it while the potatoes were cooking.
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I had changed my recipe for potatoes to save calories, as well as, to not have so much bad fat in them. I do use a small amount of mayo (fat free) instead of tons of butter or milk or other "not so good for you" ingredients all of which he cares less about.