Heat oil in a frying pan over medium heat. Add garlic and cook for 30 seconds. Add onions and cook for 2-3 minutes until golden. Add broccoli, carrots and squash buttons. Cook for 2-7 minutes or until tender. Let the mixture cool.
In a medium bowl combine the broccoli mixture with mashed potato. Preheat oven to 180°C and line a baking tray with parchment paper.
Lay out 2 sheets of puff pastry, cutting each in half lengthwise. Add the broccoli mixture along the long edge and roll the pastry over to seal. Cut into 6 small rolls. Repeat with the remaining pastry. Brush each roll with milk and sprinkle with sesame seeds. Bake for 30 minutes or until golden brown. Enjoy.