Prepare the Biscuit Dough:

1. Preheat the Oven: Preheat your oven to 400°F (200°C). Lightly grease a 9-inch pie dish or a similar-sized round baking dish.

2. Make the Biscuit Dough: In a large mixing bowl, combine the flour, baking powder, salt, and garlic powder (if using). Cut in the cold butter using a pastry cutter or your fingers until the mixture resembles coarse crumbs.

3. Add the Milk: Gradually pour in the milk and stir with a wooden spoon until the dough begins to form. Be careful not to overmix; it’s okay if the dough is slightly sticky.

4. Shape the Biscuits: Turn the dough onto a lightly floured surface and gently roll it out until it’s about 1-inch thick. Using a biscuit cutter or a glass, cut out round biscuit shapes. You should have about 8 biscuits.

5. Place in the Pie Dish: Arrange the biscuits in a circle on the prepared pie dish, ensuring they touch each other slightly. This will allow them to bake together and create a beautiful crust.

Prepare the Sausage Gravy:

6. Cook the Sausage: In a large skillet, cook the halal sausage over medium heat, breaking it up with a spoon as it cooks. Cook until browned and cooked through, about 7-8 minutes. Remove the sausage from the skillet and set it aside.

7. Make the Gravy: In the same skillet, melt the butter over medium heat. Add the chopped onion and cook until soft, about 3 minutes. Add the minced garlic and cook for an additional 30 seconds, until fragrant.

8. Create the Roux: Sprinkle the flour over the onions and garlic, stirring constantly for about 1 minute. This will create the roux for the gravy.

9. Add Milk: Gradually add the milk to the skillet, whisking constantly to prevent lumps. Bring the mixture to a simmer, and cook until it thickens, about 3-4 minutes.

10. Season the Gravy: Stir in the black pepper, salt, thyme, red pepper flakes, and nutmeg (if using). Taste and adjust the seasoning as needed.

11. Combine the Sausage and Gravy: Return the cooked sausage to the skillet, stirring to combine with the gravy. Simmer for another 2-3 minutes until everything is well combined and heated through.

Assemble and Bake the Pie:

12. Assemble the Pie: Pour the sausage gravy mixture evenly over the biscuits in the pie dish.

13. Brush the Biscuits: Brush the tops of the biscuits with the beaten egg to give them a golden, shiny finish when baked.

14. Bake the Pie: Place the pie dish in the preheated oven and bake for 25-30 minutes, or until the biscuits are golden brown and the gravy is bubbling.

15. Cool and Serve: Let the pie cool for 5 minutes before serving. Garnish with freshly chopped parsley if desired.