In a large mixing bowl, combine plain flour, salt, and ground turmeric. Cut in the cold, frozen unsalted butter and vegetable shortening until the mixture resembles coarse crumbs. Gradually add icy cold water, mixing gently, until a dough forms. Shape into a disc, wrap in plastic wrap, and refrigerate for 30 minutes.

In a skillet over medium heat, add minced beef and cook until browned, about 5-7 minutes. Stir in chopped onions, minced garlic, thyme, black pepper, curry powder, and optional cayenne. Pour in beef stock and soy sauce, simmering until thickened, about 10 minutes. Remove from heat, mix in breadcrumbs, and let cool.

Preheat your oven to 190°C (375°F). Roll out the chilled dough to about 3 mm thick. Use a round cutter to cut out circles. Place about 30 ml of cooled filling on one half of each circle, fold over, and seal with a fork.

Place the patties on a lined baking tray, brush with egg wash, and bake for 20-25 minutes until golden brown. Let cool slightly before serving.