Beat heavy cream and powdered sugar until stiff. Blend in blueberry preserves; refrigerate.
Spread butter lightly on both sides of pound cake slices. Heat grill pan or nonstick skillet over medium heat. Grill cake slices in batches until lightly browned on both sides, about 5 minutes; cool.
Stir together sliced strawberries and strawberry preserves. Cut pound cake slices in half on a diagonal. Place 4 pieces of cake in the center of a dessert plate in an overlapping fashion. Spoon one-fourth of strawberry mixture down center. Dollop with blueberry whipped cream. Garnish with decorative flag pick, if desired.