In a bowl, combine all the ingredients together. Season generously with salt an pepper. Set aside.

Preheat the oven to 375F. Line a half baking sheet with parchment and set aside.

To prepare the pastry, combine the flour, baking power, and salt in a mixing bowl. Mix to combine. Add the diced cold butter and work it into the flour until it forms hazelnut size pieces. Stream in the cold water a bit at a time until it forms into a ball of dough when pressed together.

Divide the dough into 8 pieces (more or less depending on how big you want your pasties). Roll each piece out on a lightly floured surface until it forms a thin circle.

Moisten the edges with some water and fill one side with the filling. Fold the other side of the pastry over and press it together to seal the edges. You can crimp it together with a fork or with your fingers.

Transfer the pasty to the prepared sheet pan and brush with the lightly beaten egg. Bake for 30 minutes or until cooked through and golden brown.