Blueberries can be fresh or frozen. Preheat oven to 425. Cut butter into flour in large bowl, using pastry blender or two knives, until mixture resembles coarse crumbs. Cut in cream cheese until mixture forms dough. Blend in vanilla. (Pastry may be prepared in food processor, using steel blade.) On lightly floured surface or pastry cloth, roll out 1/2 dough to 11" circle. Line 9" pie plate; set aside. Combine blueberries and cornstarch in medium bowl; toss lightly to coat. Add fruit spread and nutmeg; mix lightly. Spoon into crust. Roll out remaining dough to 11" circle; place over fruit mixture. Turn edges under and flute. Cut several slits or circle in top crust to allow steam to escape. If desired, cut leaves from pastry scraps to decorate top of pie. Bake 10 mintues. Remove pie from oven; reduce temperature to 350. Combine egg yolk and sour cream; brush lightly over crust. Return pie to oven and Cool on wire rack. Serve warm or at room temperature. Nutrition information per slice: 342 calories, 4 gm protein, 45 gm carbohydrate, 17 gm fat, 44% of calories from fat, 70 mg cholesterol, 155 mg sodium, 1-1/2 diabetic starch/bread exchange, 3-1/4 diabetic fat exchange, 1-1/2 diabetic fruit exchange.