Make this ice cream in the early months of autumn when young walnuts become available. Sometimes referred to as ‘wet walnuts’, they have a soft, creamy texture and a delicious sweet flavour; their skin is flaky and free of bitterness. Buy only the amount that you need – in their shells – as they are very perishable. I like to include as many walnuts as possible, to give the ice cream plenty of crunch and texture, but you can use less if you prefer. Chestnut honey has a pronounced flavour – slightly malty and almost bitter. It lends a distinctive note, but feel free to use a lighter, fragrant honey, such as acacia, if you prefer.