Clean leeks, cut in half lengthwise, and slice white parts (greens are not used). Wilt leek in 1 tbsp hot butter in circa 5 minutes Peel tomatoes, remove seeds, and dice. Cut olives in chunks. Mix leek, tomato, olives, cheese; add pepper to taste.
Pre-heat oven at 200 deg C (400 deg F). Line cookie tray with baking paper. Melt remainder of butter. Spread a thin layer of butter over a sheet of pastry; fold in two, spread another thin layer of butter on top, put 1/4 of leek mixture on top at short end, and fold into a triangle. Spread with butter. Repeat with other sheets of pastry Bake in oven in until golden brown (circa 15 mins).
Cut cherry tomatoes into halves. Serve triangles with cherry tomatoes and parsley.