Preheat oven to 325 degrees F. In bowl combine cherries and/or cranberries and crushed red pepper, if desired; cover with boiling water. Let stand 10 minutes; drain.
In food processor bowl combine flour, granulated sugar, cornstarch, salt, and baking powder. Add butter and soaked cherries and/or cranberries. Pulse until dough begins to clump together. Remove from processor. Gather dough and press in free-form square. Roll between two sheets parchment paper to 12x9-inch rectangle. With knife, cut thirty-six 3x1-inch pieces (do not separate). Slide parchment onto baking sheet and remove top parchment.
Bake 30 to 35 minutes or until lightly golden. Remove from oven. Cool on wire rack.
For whipped filling, in bowl combine whipping cream, cream cheese, powdered sugar, and vanilla. Beat with electric mixer on high until stiff peaks form. Refrigerate until ready to use.
To assemble, spread flat side of 18 rectangles with scant tablespoon of whipped filling. Top with remaining shortbread, flat side down.
Serve with Fudge Sauce. Sprinkle additional cherries and/or cranberries. Makes 18 sandwiches.
In saucepan combine whipping cream and corn syrup. Cook over medium-high heat until hot. Remove from heat; stir in semisweet chocolate until melted. Let cool until thick, about 1 hour.