Place powdered sugar, mascarpone cheese, 1 1/2 tablespoons liqueur, and cream cheese in a large bowl; beat with a mixer at high speed until well blended.
Brush cut sides of ladyfingers with 2 1/2 tablespoons of liqueur. Spread about 1 1/2 tablespoons mascarpone mixture over bottom half of each ladyfinger; cover with tops.
Arrange 3 filled ladyfingers spoke-like on each of 4 dessert plates. Sprinkle evenly with cocoa. Arrange 1/2 cup raspberries over each serving. Garnish with mint sprigs, if desired.