Preheat oven to 200°C fan-forced. Line 2 large baking trays with baking paper. Heat oil in a frying pan over moderate heat. Add onion, cook, and stir for 2 minutes or until soft.
Add curry paste, cook, and stir for 30 seconds or until fragrant. Add mince, cook stirring to break up lumps for 3 minutes or until browned. Stir in vegetables. Cool slightly.
Cut each pastry sheet into quarters. For each triangle, place 2 heaped tablespoons of mince mixture at the centre of the pastry square. Fold over to form a triangle. Press pastry edges together with a fork to seal. Repeat with remaining pastry and filling to make 12 triangles. Place on prepared trays, brush tops with egg. Bake for 12 minutes or until golden and puffed.