I made up a basic vanilla biscuit mix.
250g unsalted butter
140g caster sugar
1 egg yolk
300g plain flour
2tsp vanilla essence
once these were properly mixed together I split the mixture in half, and then returned half to the food processor. I added 25g of coco powder to that and remixed. Total guess work on the amount of coco, but it looks the right colour and it's the right consistency.
Then I wrapped both of the doughs in cling film and fridged them for an hour. Once the dough had cooled I rolled out both parts before layering them together. I then flattened them out some more before rolling them up into a big dough sausage. Surprisingly the vanilla dough was a little more brittle than the chocolate dough. The dough sausage was then sliced thinly and baked at 180 for ten minutes.
They came out rather well (by which I mean I mean I didn't burn them). If anything they could have used another minute or two in the oven. Mine weren't quite as delicate as the pictures I saw online, I think I need to try another cookie mix to get these totally right. They taste ok with a cup of tea.
