For the Homemade Pie Dough

1. Combine Butter with Dry Ingredients - In a large mixing bowl, whisk together all-purpose flour, sugar and salt. Add in the cold cubed butter and coat it with the flour mixture. Then use your fingertips to flatten the butter into the flour mixture.
2. Add Vinegar & Cold Water - Once the butter has been incorporated into the flour, drizzle in the white vinegar, followed by 7 to 8 tablespoons of ice cold water.
3. Combine Mixture - Gently toss everything together with your fingertips. The dough should hold when squeezed together. You can add a bit more water if it doesn't hold.
4. Roll the Dough - Turn the dough out onto a clean work surface, including any dry bits of flour. Flour your rolling pin and start rolling the dough until the butter is flattened. If the dough sticks to your rolling pin, just scrape it off and lightly add flour as needed.
5. Fold Dough - Once the butter is flattened and has incorporated with the flour, use a bench scraper and fold the dough over and onto itself. Start with the top third, followed by the bottom third and then the sides. See photos in the body of the post for reference.
6. Roll and Fold Again - Lightly flour your rolling pin and roll the dough flat one more time. Then fold it over into thirds.
7. Divide & Chill Dough - Cut the dough into 2 equal pieces. Tightly wrap in plastic wrap and chill for 30 minutes or up to 3 days. If making days ahead, let the dough sit on the counter for 15 to 20 minutes before rolling. 

For the Ham and Cheese hand Pies

1. Make Filling - Combine diced ham, shredded gouda and shredded cheddar cheese in a medium mixing bowl. Set aside.
2. Roll the Dough - Working on one piece of dough at a time. Lightly flour your work surface and use a rolling pin to roll the dough into a 12x8 inch (30x20 cm) rectangle.
3. Cut the Dough - Using a pizza cutter or sharp knife, cut into 4 equal strips, widthwise (see photo as reference). If needed, trim the irregular edges on the side.
4. Fill the Pies - Work on one strip of dough at a time. Lightly brush a border on the bottom half of the dough with the egg wash. This will give you a guide to where to place your filling and will help seal the pie. Spread 1 teaspoon of mustard within the egg wash border. Then add 1/3 cup of the filling within the border. You can cup and squeeze the filling together in between the palms of your hands to make it more compact.
5. Fold & Seal - Fold the top of the dough over and onto the filling and press to seal the edges together. Push out any air to create an airtight pocket.
6. Trim & Crimp - Using your pizza cutter or sharp knife, trim the top and bottom edges. This will help the pies puff up nicely when it bakes. Then use a fork to crimp a decorative edge on the pies. Make the remaining 3 pies and then make 4 more pies with the other piece of dough.
7. Freeze - Transfer the assembled pies onto 2 large baking sheets lined with parchment paper. Freeze for at least 30 minutes before baking. If you do not have space in your freezer you can refrigerate the pies for at least 1 hour before baking.
8. Preheat Oven - Set a rack in the center of the oven and preheat it to 400ºF (204ºC).
9. Egg Wash & Vent - When ready, bake 4 pies on one baking sheet at a time. Keep the other pies in the freezer or fridge to bake after. Cut 3 slits to vent the top of the pies, then lightly brush with the egg wash and then top with poppy seeds if you'd like.
10. Bake - Bake for 21 to 25 minutes or until the tops are golden brown. Transfer to a wire rack and allow to cool for 10 minutes before serving. Enjoy!