Preheat oven to 375 degrees F. Place tart shells in a 15x10x1-inch baking pan. In a small bowl combine egg white and water. Brush beaten egg white over crusts. Bake for 5 minutes; set aside to cool.

For filling, in a large bowl combine sweet potatoes and whipping cream; mash and stir until smooth. Stir in maple syrup, egg yolks, and pumpkin pie spice. Spoon filling evenly in tart shells. Bake for 30 minutes. Cool on a wire rack for 2 hours.

Meanwhile, preheat broiler. For meringue, in top of double boiler combine sugar, 4 egg whites, vanilla, and salt. Beat with electric mixer on low speed for 30 seconds. Place over boiling water (upper pan must not touch water). Cook, beating constantly with electric mixer on high speed, for 8 to 10 minutes or until mixture is fluffy, holds soft peaks, and reaches 160 degrees F on instant read thermometer. Remove from heat. Beat 30 seconds more, scraping sides and bottom of pan.

Mound meringue mixture on baked pies, forming peaks. Broil 5 to 6 inches from heat for 1 to 2 minutes or until tops are lightly browned. Cool on wire rack for 10 minutes before serving. Cover and refrigerate to store. Makes 12 servings.

Prepare as directed above except use a purchased 9-inch graham cracker crumb pie shell instead of tarts. Spoon filling into pie shell. Bake for 60 minutes or until filling is set (160 degrees F). Mound all the egg white mixture atop the cooled pie. Broil 5 to 6 inches from the heat for 1 to 2 minutes or until top is lightly browned. Let stand 10 minutes before serving.