Finely chop mushrooms and onions by hand or in a food processor. Heat 1 tablespoon oil in a large non-stick frying pan over high heat. Add the mushrooms and onions and cook, stirring for 8 minutes until all of the moisture has evaporated. Stir in herbs. Set aside to cool for 15 minutes (mixture must be cool – you can not add warm mushrooms to cold mince mixture). Drain any excess moisture and transfer to a bowl.
Add mince, egg and breadcrumbs to mushroom mixture. Mix until well combined.
Preheat oven to 220°C/200°C fan-forced. Line 2 baking trays with baking paper.
Spread dip evenly over 3 pastry sheets, leaving a 2cm border at ends furthest away from you.
Divide mince mixture over dip, using fingertips to help make an even layer. Sprinkle evenly with cheese. Roll up as tightly as possible. Chill for 10 minutes before slicing each roll into 12. Place on trays, cut-side down, allowing room for spreading. Bake for 15-20 minutes until golden and mince is cooked through. Cool slightly before serving.