Melt the butter in a small pan. Take half a sheet of filo pastry and brush lightly with the melted butter. Fold in half lengthways. Place a spoonful of the filling at one end, and fold over the corner to enclose the filling. Keep on folding in the shape of a triangle. Tuck the last piece into the last fold, and place, seam side down, on a baking tray lined with greaseproof paper. Bake in the oven for 15 mins until golden brown.