Combine flour and salt. Cut the butter into small cubes and cut it into the flour. Mix in the ice water. Form the rough dough into a rectangle, wrap and refrigerate at least 30 minutes.
Roll the dough into a rectangle. Fold both ends to meet in the middle and fold together like a book. Press together, wrap and refrigerate for 30 minutes. Repeat this process twice more and refrigerate for at least 30 minutes.
Preheat the oven to 400 degrees. Roll the dough into a 1/4 inch thick, 14x7 rectangle. Trim off any uneven edges. Place the dough on a lined sheet pan. Mark a 1 inch border around the dough. Pierce the inside of the rectangle with a fork. Spread the cheese filling inside of the border. Layer the pumpkin and potato on top of the cheese. Brush the exposed edges with egg wash and bake for 40 minutes. Until the edges are brown and the potato and pumpkin are tender. Cut into 8 Portions, sprinkle with rosemary, and serve.