MacEggs, didn't use a mandolin, just my wife's careful hands. I told her she was taking too long, but then again, that's why the slices look so nice! This is our go to potato method now. I saw someone here did something like this over a year ago and now we love it. We put butter on top so it melts all down in there and the potatoes get crispy on the bottom and the onions tucked in between caramelize. Just started with the sweet potatoes the last few times. I love that even more.