1.Heat half the butter in large frying pan; cook garlic and leek, stirring occasionally, until leek softens. Stir in caraway seeds; cook, stirring, 2 minutes.
2.Combine leek mixture and cheeses in medium bowl.
3.Preheat oven to 200°C/400°F. Oil oven tray.
4.Melt remaining butter in small saucepan. Brush one sheet of fillo with butter; fold in half lengthways. Place a quarter of the leek mixture at bottom of one narrow edge of fillo, leaving a 1cm (½-inch) border. Fold opposite corner of fillo diagonally across the filling to form a triangle; continue folding to end of fillo, retaining triangular shape. Place on tray, seam-side down. Repeat with remaining ingredients to make four triangles in total. Brush triangles with butter; sprinkle with sesame seeds.
5.Bake triangles about 10 minutes or until browned lightly