You expect to pay a bit extra for lamb. It is expensive but our Irish lamb is exceptionally good. And well done to the many farmers who produce it. What we produce is very hard to beat. Slow roasting it with a little stock in the bottom will ensure it stays wonderfully moist. Also keep in mind that this mixture of herbs works well with a rib roast if you prefer it. There is no cream in this recipe. I like the lightness and tartness of the creme fraiche.This gratin just needs four ingredients and a little salt and pepper to make the most delicious side dish. A mandolin is very handy for slicing them. You will spend about €50 on one but it is a very handy piece of equipment to have in your kitchen. Once the potatoes are sliced, the gratin comes together quickly and then bakes unattended in 90 minutes at the same temperature as the lamb.