Combine the white wine, cider vinegar, cream, 3 cups water and diced leek/onion in a bowl. Whisk to combine.
Combine the garlic, Hungarian paprika, smoked paprika, cumin, pepper and salt. Rub the mixture all over the pork shoulder.
Place pork in a crock pot slow cooker and pour in the liquid mixture. Cook for 4 to 5 hours on medium heat or until the meat falls off the bone.
Reserve the liquid and leeks/onions and set aside. Shred the pork meat, discarding fat and bone. Cool at room temperature, then place meat and cooking liquid in the refrigerator to chill. Can be done one day ahead.
When ready to finish the pies – Cook the diced sweet potato in simmering water until a paring knife easily goes through them. Drain and set aside.
The shredded pork may yield more meat than needed for the recipe. Place 8 cups of the shredded meat in a large mixing bowl. Keep any remaining meat for another use. Toss with the reserved cooking liquid and cooked diced sweet potatoes.
Preheat oven to 350 degrees. Roll out two 10-inch rounds of dough. Line two nine-inch pie pans. Divide the filling into the two lined pie tins.
Combine the remaining egg yolks with the remaining 2 tablespoons water. Roll out two more 10-inch rounds of dough. Using a pastry brush, brush the rim of the bottom pie dough. Place the top dough rounds on top and press lightly on sides. Trim sides and crimp. Using a paring knife, slash two steam vents in each pie top. Brush the entire top of the pie with the egg water glaze and sprinkle with the coarse sea salt.
Bake in the preheated oven for 50 to 60 minutes or until the top of the crust is nicely browned. Let rest 30 minutes; then serve.
Makes two 9-inch double-crusted pies