These are a really nice tasting biscuit that has the flavour of walnut and rosemary. they can be eaten with a soft mild cheese or just as nice on their own.
In a food processor, blitz the flour and butter to a breadcrumb stage. Add the yolks, sugar and rosemary and blitz again briefly to form a dough. Empty the dough on to a floured surface and gently knead the walnuts into the dough. Shape into a sausage approximately 4-5 cm in diameter, wrap in cling wrap and chill for an hour or so.
While the dough is chilling, heat your oven to 170C. Remove the dough log from the fridge, unwrap and slice it into biscuits roughly 1/2cm thick and place on a baking sheet lined with baking paper. Sprinkle with the flaked sea salt.
Bake for 17 minutes or until the edges start to turn golden. These biscuits don't spread much, if at all, so you can bake quite a few at a time. Once out of the oven , leave them for 5 minutes on the baking sheet before gently removing them to a rack to cool completely.