In a large mixing bowl, combine all-purpose flour and salt. Cut in unsalted butter using a pastry cutter until it resembles coarse crumbs.

Gradually mix in cold water, stirring gently until a soft dough begins to form. Knead lightly for about 1 minute until smooth.

Wrap the pastry in plastic wrap and refrigerate for 30 minutes.

In a large skillet, heat olive oil over medium heat. Sauté onion and garlic for 3-4 minutes until softened.

Add carrot and potato, cooking for 5-7 minutes until tender. Stir to prevent sticking.

Mix in peas, thyme, and rosemary. Season with salt and pepper. Cook for another 2 minutes and cool significantly.

Preheat your oven to 400°F (200°C). Roll out the chilled dough to 1/8 inch thick and cut out circles.

Place a spoonful of filling on each circle, fold over, and crimp edges securely with a fork.

Arrange on a lined baking sheet and brush with egg wash if desired.

Bake for 25-30 minutes or until golden brown and flaky. Cool for 5-10 minutes before serving.