The key words in the recipe above is "as needed"--and a bit less always worked for my grandmother, my mother, myself and probably my kids who are also great cooks. A roux works for me too, with a portion of it on each layer, and a bit of extra milk over all. The milk provides the browned skin over all the potato slices. Today, we rarely peel potatoes, and they are most often "organic" so sliced,well-scrubbed, unpeeled but "edited" from zits and eyes, works. To get to au gratin, just cover the dish for the last 20-25 mins. of cooking with your favourite grated cheese mixture. Hey, works for us!