Bake pastry 2 minutes. Reduce oven temperature to 375F. and bake until pastry is golden brown and firm to touch, about 40 minutes longer. Turn off heat. Leave pastry in oven 5 minutes. Remove from oven. Carefully remove pastry from parchment. Using serrated knife, cut pastry in half horizontally. Arrange cut sides up on rack (pastry will appear moist and slightly doughy inside). Cool completely. Fit clean pastry bag with 3/4-inch (no. 7) star tip. Transfer filling to bag. Place pastry bottom on platter. Pipe filling into pastry in large circular mounds. Set top of pastry over filling. Dust lightly with powered sugar. Gently heat sauce in heavy small saucepan. Mix in rum. Using serrated knife, cut pastry into wedges. Serve, passing sauce separately. Serves 8. Bon Appetit May 1991