Wrap dough in plastic wrap and place in refrigerator overnight to soften.
Preheat oven to 350°F. Unwrap dough, and on a lightly floured surface, roll out to 1/4-inch thickness. Cut into six portions and stretch each by hand into a rectangle approximately five by seven inches.
Place 1/4 cup sandwich ingredients in the bottom center of each dough rectangle. Fold top half over bottom half and use a fork to crimp edges together, sealing pockets shut.
Create an egg wash by whisking egg with milk or water. Brush mixture over pockets. If desired, sprinkle nuts or seeds on top.
Place pockets on a parchment-lined cookie sheet and bake for approximately 25 minutes, or until golden brown.