1.In a large saucepan, heat oil on high. Saute onion, garlic, and seasoning 2-3 minutes, until onion is tender. Add lamb and cook 5-6 minutes, stirring, until evenly browned.
2.Stir in stock and zest. Reduce heat to medium. Simmer, covered, 1 hour. Remove lid and simmer a further 25-30 minutes, until lamb is tender and sauce thickened. Allow to cool.
3.Preheat oven to 180°C. Line a 20cm round pie dish with shortcrust pastry, joining sheets to fit. Trim edges. Fill with scrunched foil. Bake blind 10 minutes, until golden. Remove foil.
4.Increase oven to 200°C. Spoon filling into pastry. Sprinkle with coriander.
5.Join puff pastry sheets together and trim to a circle large enough to cover pie filling. Position on pie, pressing around edges to seal. Brush with egg and sprinkle with seeds. Make an air vent in centre with a sharp knife.
6.Bake 15-20 minutes, until puffed and golden. Serve in wedges with roast pumpkin.