1. Mix cranberries and 1 cup sugar in saucepan. Cover; cook, stirring occasionally, over medium-high heat 20 minutes, until thick and berries pop. Let cool.
2. Heat oven to 400 degrees F. Roll out piecrust to fit 9-inch pie plate. Transfer into plate; flute edge. Prick crust with fork. Line with aluminum foil; fill with dried beans.
3. Bake in 400 degree F oven for 10 minutes. Remove foil and weights. Brush crust with egg.
4. Whisk remaining 3/4 cup sugar and cornstarch in large bowl. Add pistachios, apple and sour cream. Add cranberry. Scrape into crust. Place plate on baking sheet for drips.
5. Bake in 400 degree F oven 50 minutes or until bubbly. After first 20 minutes, cover edges of crust with foil to prevent overbrowning. Cool on rack. Serve with ice cream if desired. Makes 12 servings.