Philadelphia Chocolate Royale Cheesecake

Crust:

18 Oreo cookies, finely crushed

2 tablespoons butter, melted

Filling:

1 (4.00 ounces) package cream cheese, softened

1 cup sugar

1 teaspoon vanilla

1 (8.00 ounces) package baker semisweet baking chocolate, melted & slightly cooled

1/4 cup hazelnut-flavored liqueur (optional)

4 eggs

Crust: Mix together cookie crumbs, sugar and butter; press into the bottom of a 9" springform pan. Bake at 325 degrees for 10 minutes. Filling: Mix together cream cheese, sugar and vanilla with an electric mixer until well blended. Add chocolate, liqueur and eggs; mix just until blended. Pour over the crust. Bake at 325* for 55-60 minutes or until the center is almost set if using a silver springform pan (bake at 300 degrees for 60-65 minutes or until center is almost set if using a dark nonstick springform pan). Run a knife or metal spatula around the rim of the pan to loosen the cake;  cool before removing the rim of the pan. Refrigerate for 4 hours or overnight.