In a large mixing bowl, combine ricotta cheese, confectioners' sugar, sour cream and coffee liqueur; mix well. Set aside. In an electric blender or food processor container, process cookies, in small batches, until finely crushed. Remove 6 cherries from cherry filling; reserve for garnish. To assemble dessert, spoon 2 tablespoons ricotta cheese mixture into each of six (8-ounce) parfait glasses. Add 2 tablespoons cookie crumbs to each glass; top each with 2 tablespoons cherry filling. Repeat ricotta, crumb and cherry layers. Finish each serving with an equal portion of the remaining ricotta cheese mixture. Garnish with reserved cherries, grated chocolate and mint leaves, if desired. Let chill 2 to 3 hours before serving. Serves 6