1.Preheat oven to 180°C (160°C fan forced).
2.Heat a heavy-based flameproof baking dish over high heat until almost smoking. Season duck, place in dish, skin-side down. Cook 2 minutes or until skin is crisp, turn, cook until browned. Remove from dish.
3.Add bacon to same dish, cook, stirring, until crisp. Add carrot, celery and leek, cook, stirring, until softened. Return duck to dish with rosemary and bay leaves. Add wine, bring to the boil. Add stock, return to the boil. Cover, bake 1½ hours or until duck meat shreds easily with a folk. Discard herbs. Shred duck.
4.Increase oven to 200°C (180°C fan forced).
5.Meanwhile, heat butter in a large frying pan over high heat, cook mushrooms, stirring, until golden.
6.Transfer baking dish from oven to high heat, stir in mushrooms and shredded duck. Blend flour with a little of the cooking liquid in a small bowl until smooth, stir into dish until mixture boils and thickens. Spoon mixture into a deep 2-litre (8-cup) pie dish, cool slightly.
7.Cut pastry to fit pie dish, crimp edge with your fingers or a fork to seal. Brush pastry with egg.
8.Bake pie for 15 minutes until pastry is browned.