1.Heat oil in large frying pan; cook onion and anchovy, stirring, about 5 minutes or until soft. Add cumin, tuna, egg, parsley and mint; cook, stirring, about 30 seconds or until egg starts to set. Remove from heat, season to taste; cool.
2.Preheat oven to 200°C/400°F. Oil oven trays; line with baking paper.
3.Brush 1 sheet of pastry with butter; top with two more sheets, brushing each with butter. Cut layered sheets crossways into 5 strips. Place 1 rounded tablespoon of tuna mixture at one short end of each pastry strip. Fold one corner of pastry diagonally over filling to form a triangle. Continue folding to end of strip, retaining triangle shape. Repeat to make a total of 20 triangles.
4.Place triangles on trays; brush with remaining butter, sprinkle with poppy seeds. Bake triangles about 20 minutes or until browned lightly.