- Preheat oven to 220 degC. Heat butter in frying pan.
- Add onion and fry gently for 2 minutes.
- In a bowl, mix mushrooms, mince, salt and pepper and breadcrumbs. Shape into a roll.
- Roll out pastry into a rectangle on floured board. Pop the meatloaf at one end and roll up, like a large sausage roll.
- Secure the ends and press together. You may have to trim the pastry.
- Place on a greased tray seam-side down, brush with beaten egg and slash a few cuts in the top to let hot air escape.
- Bake for 35 to 40 minutes or until pastry is golden brown.