Onion squash, which has a deep and not-too-sweet flavour, is my favourite squash variety; its thin skin is best left on during roasting. Mâche, also known as lamb’s lettuce, is slightly crunchy and has a very clean flavour. Tossed together in a hazelnut vinaigrette with crunchy toasted hazelnuts, these ingredients marry beautifully, creating a delicious and unusual accompaniment for lamb.