• In a large skillet over medium heat, sauté the chopped onions in a drizzle of oil until translucent and just beginning to caramelize, about 5–7 minutes. Add the garlic and cook for an additional 1 minute until fragrant.
• Add the game sausage mince, breaking it up with a wooden spoon, and cook until browned and cooked through—about 8–10 minutes. Stir in thyme, tomato paste, salt, and pepper, cooking for another 2 minutes.
• Pour in the beef stock and Worcestershire sauce. Simmer uncovered for 10–15 minutes, until the mixture thickens slightly and becomes glossy. Set aside to cool completely.

Prepare the Pastry:

• In a large mixing bowl, combine the flour and salt. Add the cold butter and rub it into the flour using your fingertips until the mixture resembles coarse crumbs. Stir in ice water gradually and form into a dough. Wrap and chill for 30 minutes.
• Preheat the oven to 375°F (190°C). Roll out 2/3 of the chilled pastry on a floured surface and use it to line a 9-inch pie dish. Fill with the cooled meat mixture.
• Roll out the remaining pastry for the top crust. Lay it over the filling, trim and crimp the edges. Cut slits for steam.
• Whisk the egg and milk together and brush over the crust. Bake for 50–60 minutes, or until crust is golden and filling is bubbling.