2 packages (16 ounces total) cream cheese, room temperature
Combine cream cheese and cottage cheese in a large mixing bowl; beat until smooth. Gradually add sugar, beating well. Add eggs and beat until well blended. Add cornstarch, flour, lemon juice, and vanilla; stir well. Add melted butter and sour cream, beating until smooth.
Pour filling into 10-inch springform pan with graham cracker crust (below). (Place a shallow baking pan on the bottom rack of the oven with about an inch of hot water.) Bake cheesecake in center of oven at 325° for about 70 minutes, or until firm around edges. Turn off oven and let cheesecake cool with oven for 2 hours. Remove from oven and cool completely. Remove from pan; refrigerate. When completely chilled, top with blueberry glaze (below).
In a 1-quart saucepan combine sugar and cornstarch. Stir in water. Crush 1/2 cup blueberries; add to sugar and water mixture. Cook over medium heat, stirring constantly, until mixture is thickened and begins to bubble. Continue to boil gently for about 2 minutes, or until blueberry glaze mixture is clear. Cool completely. Arrange remaining blueberries over the top of the cheesecake. Pour cooled blueberry glaze over berries. Keep blueberry cheesecake tightly covered in refrigerator.