Leg of Lamb on a Bed of Potatoes

When cooking the leg of lamb - or another roast — separately from the potatoes, I often spread a layer of creamed sorrel (raw sorrel chiffonade, salted, cooked slowly in butter until melted, cream added and slightly reduced) over the potatoes’ surface before putting them to bake.

Try to use a variety of potato that does not disintegrate during cooking. The texture of the gratin is most attractive when large potatoes are used, sliced as thinly as possible, lengthwise. The traditional