PREHEAT oven to 375° F. Grease 9-inch spring form pan.
COMBINE graham cracker crumbs and butter in medium bowl; stir until crumbly. Press onto bottom and 1 inch up side of prepared pan.
BEAT cream cheese and sugar in large mixer bowl until creamy. Add eggs one at a time, beating well after each addition. Stir in liqueur.
COMBINE 1/2 cup morsels and flour in small bowl; gently stir into cream cheese mixture. Pour into crust. Sprinkle remaining morsels on top.
BAKE for 40 to 50 minutes or until edge is set but center still moves slightly. Cool in pan on wire rack for 10 minutes. Loosen side of pan. Cover; refrigerate for at least 3 hours. Garnish with whipped cream and chocolate curls, if desired.
FOR SENSATIONAL MOCHA CHEESECAKE:
SUBSTITUTE 1/4 cup half-and-half or milk, 2 tablespoons cooled coffee and 1 teaspoon almond extract for liqueur. Prepare as above.