Prepare the Pastry Dough:

1. In a large mixing bowl, combine flour and salt.
2. Add chilled butter pieces and use a pastry cutter or your fingers to blend until the mixture resembles coarse crumbs.
3. Gradually add ice water, mixing until the dough starts to come together. Add more water, a tablespoon at a time, if necessary.
4. Form the dough into a ball, wrap it in plastic wrap, and refrigerate for at least 30 minutes.

Prepare the Filling:

1. Choose your desired filling (savory or sweet).
2. For savory fillings, mix the ingredients in a bowl and season with salt and pepper.
3. For sweet fillings, combine ingredients in a bowl.

Assemble the Pastries:

1. Preheat oven to 375°F (190°C). Line a baking sheet with parchment paper.
2. On a lightly floured surface, roll out the chilled dough into a large rectangle, about 1/8 inch thick.
3. Spread the filling evenly over the dough, leaving a small border around the edges.
4. Starting from one long side, carefully roll the dough into a tight log.
5. Cut the log into 1-inch pieces and place them, seam side down, on the prepared baking sheet.

Bake the Pastries:

1. Brush the tops of the pastries with the beaten egg wash.
2. Bake for 15-20 minutes, or until golden brown and crispy.
3. Let the pastries cool slightly before serving.