Blend the olives in a food processor. Mix them with the onion and the spearmint.
Prepare the dough by placing the liquids in a bowl and adding flour until you have a soft dough that doesn't stick. Set it aside to rest for 15 mninutes.
Roll out the dough in filo sheets that are almost square, then divide the filo sheet into 4 quarters and each quarter into 2 triangles. Starting from the base of the triangly, place a spoonful of filling, then fold the ends inwards and roll towards the top point, like a small croissant.
Place them in a baking tray lined with greaseproof paper and bake at 180°C until golden brown.