In large bowl, stir together 1 1/2 cups flour and salt. Using pastry blender or fork, cut butter and shortening into flour until mixture resembles cornmeal. Add 3 tablespoons cold water and stir. If the dough is still dry, add additional water until mixture holds together in large clumps. Shape dough into a disc, cover with plastic wrap and refrigerate at least 1 hour.
Preheat oven to 375°F. Line cookie pan with parchment paper. Roll dough to a 12-inch circle, about 1/8 inch thick and transfer to pan.
In large bowl, toss plums, sugar, cinnamon, lemon juice, zest and 1 tablespoon flour until well combined. Spoon plum mixture over dough, leaving a 2 inch border around the edges. Sprinkle pistachios over the filling. Fold edge of dough over fruit filling, pleating together every few inches. Brush edges of dough with egg wash, and sprinkle with Wilton Sparkling Sugar. Bake 45-55 minutes or until crust is golden and fruit juices begin to bubble. Cool to room temperature on cooling grid.
In a small bowl, heat apricot preserves and water in microwave for 10 second intervals until very warm, stirring until smooth. Brush over plums.