Preheat the oven to moderately hot (200°C/180°C fan-forced). Grease a 24cm springform pan.

Heat half the oil in a large saucepan, cook the chicken, in batches, until browned. Heat remaining oil in same pan, cook kumara, uncovered, until browned. Return chicken to pan.

Add simmer sauce and cream to chicken mixture. Bring to the boil; reduce heat simmer, partially covered, for 15 minutes or until sauce thickens and chicken and kumara are cooked. Stir in coriander and salt and pepper to taste. Cool.

Meanwhile, layer 3 sheets of pastry, brushing each with some of the butter. Fold in half lengthways, place across the base and up the side of the prepared pan with edges overhanging. Repeat with another 9 sheets, overlapping strips clockwise around pan until covered.

Spoon chicken mixture into pan, trim pastry to be level with top edge of pan. Layer remaining 3 pastry sheets, brushing with butter. Fold in half crossways. Place pastry on top of pie, trim pastry to a round a little larger than the pan. Tuck pastry edge down sides of pan, brush top with butter. Place pie on an oven tray.

Bake for about 45 minutes or until boiled. Stand 15 minutes before cutting.