In a medium saute pan over medium heat, melt 4 tablespoons butter, add ginger and cook for 1 minute. Add in brown sugar, cinnamon and nutmeg. Let cook 2 minutes, then add in fruit, stirring gently to combine. Let cook over medium heat to gently caramelize, about 6 to 8 minutes. Remove fruit from pan, reserve sauce in pan. Let fruit cool to room temperature. Place puff pastry dough on baking sheet. Spread fruit out on puff pastry dough, leaving a 2-inch border all around. With the long end closest to you, fold dough into thirds, then repeat ending with the seam down. Pinch short ends closed. Brush with egg yolk.
Bake until golden brown and crispy, about 20 to 25 minutes. While baking, heat up remaining sauce over medium heat, fortify with rum and 2 tablespoons butter. To serve, remove strudel from oven and slice immediately into 6 pieces. Drizzle some of the sauce on dessert plates. Place strudel slice on top and dust with powdered sugar.