1.Preheat oven to 200°C/180°C fan-forced. Grease 12-hole (⅓-cup/ 80ml) muffin pan.
2.Cook bacon in heated frying pan until just cooked; drain.
3.Heat 30g of the butter in same pan; cook mushrooms, stirring, until browned. Stir in sauce.
4.Melt remaining butter. Brush one pastry sheet with butter, top with another sheet. Repeat with two more sheets of pastry. Cut through the four layers of pastry into 10cm squares. Place one square diagonally over another to give eight points. Press pastry into one pan hole. Repeat with remaining pastry sheets and butter.
5.Break eggs into pastry cases, top with mushroom mixture and bacon.
6.Bake tarts 20 minutes or until pastry is browned. Just before serving, sprinkle tarts with chives and freshly ground black pepper.