In the bowl of a food processor, combine the flour and kosher salt. Pulse once or twice to mix. Add the diced cold butter and pulse several times until the butter resembles small peas. Pour the ice water into the food processor while pulsing. Continue pulsing until the dough begins to stick together in small clumps. Check the dough – it should stick together if you squeeze it.
Dump the dough mixture onto the counter and use your hands to press it together. Divide the dough in half and shape each piece into a flat disc. Cover with plastic wrap and chill for at least 1 hour.
Pork, Leek, and Potato Pie
Peel and dice the potatoes. Add the potatoes to a large pot along with a generous pinch of salt. Place over high heat and bring to a boil. Cook the potatoes for 15 to 20 minutes until tender. When the potatoes are tender, drain and return to the pot. Mash the potatoes then transfer to a mixing bowl and allow to cool completely.
Place a non-stick skillet over medium high heat. Add 1 tbsp of olive oil to the skillet. Crumble the ground pork into the pan and let cook for a few minutes. Break up the ground pork with a spatula, and continue cooking until browned, stirring occasionally. Season with 1/2 tsp kosher salt and continue cooking until the pork begins to brown. Drain any excess liquid or fat from the pork and set aside.
Wipe the skillet clean and return to the stove. Add 1 tbsp of butter along with the chopped leeks. Sauté over medium heat until the leeks soften and begin to brown. Add the minced garlic along with the chopped thyme and sage and sauté for 1 minute. Return the pork to the pan and add the nutmeg, remaining 1/2 tsp kosher salt, and pepper. Cook for another minute and then remove from the heat to cool.
In a mixing bowl, combine the pork and leek mixture with the cooled potatoes along with the grainy mustard. Mix until the potatoes are fully combined with the pork. Let cool to room temperature before filling the pie.
Preheat the oven to 375°F. Lightly grease a 9” pie plate. On a lightly floured surface, roll one disc of dough out into a circle. The dough should be around 2 inches wider than the pie plate on all sides. Carefully fold the dough in half then lift it into the pie plate. Unfold the dough and arrange it in the pie plate letting the excess hang over the edges.
Spoon the filling into the pie crust and smooth the top. Roll out the remaining disc of dough into a circle that is a little wider than the pie plate. Brush the bottom edge of the pie crust with the beaten egg. Place the top crust over the pie and press down to seal the edge. Trim the excess pie dough around the edge and crimp to create an attractive crust. Brush the top of the crust and the crimped edges with the egg wash. Cut several slits in the top crust for steam to escape.
Bake the pie for 45 to 55 minutes until the pastry is golden brown and fully cooked. The filling is already cooked so it's just the pastry that needs to be cooked through.
When the pastry is golden brown, remove the pie from the oven. Allow the pie to cool for about 15 minutes to make slicing easier. This pie can be eaten either warm or cold. Enjoy!