Preheat oven to 400 degrees. Prepare a non stick baking sheet or line a baking sheet with parchment paper. Place puff pastry on the baking sheet and unfold the sheet, brushing the surface with melted butter. Arrange sliced star fruit in the center of the puff pastry and drizzle lime juice over the star fruit. Spread raisins and cashews evenly over the star fruit and drizzle fruit liquor over the filling.
Fold over one side of the puff pastry and brush with egg white. Fold over the other side and brush with egg white. Cut thin slits on top to allow steam to escape. Bake in the middle of the oven for 20 minutes and then place on the upper rack for an additional 10 minutes for browning. Dust with confectionary sugar over the top and serve with plantain sauce.
Melt butter and sauté plantain for approx 2 minutes. Add brown sugar and cook over medium heat until the sugar melts and the sauce thickens. Drizzle over strudel or serve on the side of the strudel.