In medium-size saucepan, mix granulated sugar and cornstarch until blended; stir in 3 cups of the raspberries. Bring to a boil over medium-high heat; boil 2 minutes or until thickened. Cool to room temp; add remaining 1 cup berries.

In large bowl, beat with electric mixer cream cheese, confectioners' sugar and liqueur until smooth. Stir in sour cream.

Separate and arrange half the ladyfingers on bottom of 9-inch square glass baking dish, overlapping slightly. Spoon half of the raspberry mixture (1 cup) on top, then half the cream cheese mixture (1-1/2 cups). Sift half the cocoa powder on top; repeat layering as above, ending with cocoa powder.

Cover with plastic wrap; refrigerate at least 4 hours or overnight. Garnish with mint and raspberries, if desired.