MIX crumbs, 1/4 cup of the sugar and the butter; press firmly onto bottom of 9-inch spring form pan.
SPRINKLE gelatin over 1/4 cup of the water in small saucepan; let stand 1 min. Cook on low heat 3 min. or until gelatin is completely dissolved, stirring constantly.
BEAT cream cheese, remaining 1-cup sugar and the cocoa in large bowl with electric mixer on medium speed until well blended. Gradually add gelatin mixture, remaining 1/4-cup water and the liqueur; refrigerate until slightly thickened. Gently stir in the whipped topping; pour over crust. Refrigerate several hours or until firm. Top with chocolate curls just before serving. Store in refrigerator