Potato and Kohlrabi Gratin with Lemon Thyme

A mandolin really helps to get the potato and kohlrabi slices as thin as possible and will speed up the cooking time. Lemon thyme is quite unusual; use ordinary thyme if you can–t find any but lemon thyme has a delicate favour that’s especially suited to summer dishes. It’s a good one to plant, or keep a small pot of it. Serve this as a side dish – it’s particularly good with pork, or as a vegetarian main course with steamed summer greens.