I treated myself to the latest Great British Bake Off recipe book since it was only £7 at a Book People book sale at work. This was when the series was only part-way through and I wasn't sure what they would be making each week though the recipes in the book do give a clue. I really liked the look of the pistachio and white chocolate churros, which I think I remember were made by Jane, the eventual runner-up of the show.
The full recipe is available on the BBC Food website which is helpful as it would have taken me ages to write out everything I did! I consider myself a fairly proficient baker, but I found these really hard - not to make as much as to assemble.
The book had a good explanation of how to shell pistachios; after you remove the hard shell there is still a brown skin covering the green nut. Bring the pistachios to boil in a pan of water and simmer for ten seconds; drain them in a sieve then rub with kitchen paper or use your fingers and the brown skins come off easily.
When I made the pistachio custard and pulsed the nuts in a food processor, I just couldn't get them smooth enough, so my custard was quite lumpy, even after I sieved it.