Puree raspberries in a blender or food processor until smooth. Press through a mesh sieve to remove seeds. Pour puree into a measuring cup and add enough water to make 1 cup, if necessary. Whisk raspberry puree, sugar and cornstarch in a small saucepan until blended. Bring to a boil over medium-high heat and cook, stirring constantly, 1 to 2 minutes or until slightly thickened. Remove from heat and let cool.
Chocolate Graham Crust
Preheat oven to 350°F. Pulse graham crackers, pecans and sugar in a blender or food processor to make fine crumbs. Add 2 tablespoons raspberry sauce and melted butter; pulse or stir until combined. Press mixture onto bottom of 9 x 3-inch springform pan with removable bottom. Bake 10 minutes. Cool completely. Reduce oven to 325°F.
Combine cream cheese, sugar, sour cream and cornstarch in a large mixing bowl. Beat with an electric mixer on medium speed 2 minutes. Beat in eggs one at a time. Stir in Grand Marnier and vanilla; pour into prepared crust.
Set the springform pan on a piece of wide heavy-duty aluminum foil. Fold the foil carefully up the sides of the pan without tearing it. Set the pan in a large baking dish or roasting pan and place on oven rack. Pour in enough boiling water to reach halfway up sides of the springform pan.
Bake 1 hour at 325°F. Turn off oven and prop the door ajar with the handle of a wooden spoon. Let cool in the oven for 1 hour. Remove from oven and cool completely. Remove from springform pan.
Heat remaining raspberry sauce in a microwave-safe bowl on high (100 percent) power 30 seconds, or just until warm. Spread evenly over top of cheesecake; refrigerate 1 hour.
Raspberry Cheesecake Topping
Top cheesecake with remaining raspberries and dust with confectioners' sugar.
Lighten Up Tip To reduce fat, substitute reduced-fat sour cream, egg substitute for large eggs and 2 packages (8 ounces each) reduced-fat cream cheese for 2 packages (8 oz. each) cream cheese.