I like to use recipes more as a starting point and technique guide than as instructions or rules, and fitting them to what I have and not stressing out too much about exact ingredients or quantities. This is why I'm not big on baking like my friend Kim, who is a baking bad-ass.
I saw this post on Smitten Kitchen for a gorgeous sorta-not-really gratin potato dish and had to try it. Had to. But didn't. For months. Until my friends and I had a steak night. Steak is a great reason to make delicious things happen with potatoes.
Pictured are russet potatoes with red onions crammed in between them, and butter shmeared over the whole thing. The recipe didn't call for it, but I added a splash of milk to the bottom of the baking dish. It just felt right (and it was-- the milk made the potatoes soft and creamy). I used rosemary instead of thyme because that's what I had on hand. I think thyme would have been better, but my thyme died soon after my third move last year. Alas.