For the pastry place the flour, baking powder, salt, butter and egg yolk into a mixing bowl. Knead for 2 Minutes. While kneading, add 60 g water in a thin stream until the mixture resembles a dough. You may not need all the water
Remove from the bowl and form into a ball. Wrap in clingfilm and chill for 30 minutes
Cook at around 200
To make the tart shell, remove the dough from the fridge and place on a floured surface. Roll out to a large square and cut to fit tart cases. Prick the bottom with a fork and chill for 15 minutes. Then cover with a piece of greaseproof paper and fill with baking beans (or rice)
Blind bake for 15 minutes, then remove the beans and greaseproof paper and bake again for a further 5 minutes
Meanwhile to make the tart mixture, in a mixing bowl crack the eggs, grate the Gruyere and then pour over the double cream in the mixing bowl. Whisk until combined and leave to one side.
To assemble the tart, pour the cream mixture until three quarters full. Crumble feta over the top and add the kalamata olives.
