1-First, prepare the lamb shanks by seasoning and searing them in a hot pan until browned on all sides to lock in flavor, then set aside.

2-Next, in the same pan, sauté chopped onions, garlic, and mushrooms until softened and fragrant, adjusting seasoning.

3-Then, sprinkle flour over the vegetables, stirring to form a roux, then gradually add beef or lamb stock to create a thick sauce.

4-After that, return the lamb shanks to the pan, cover, and simmer gently for about 1.5 to 2 hours until the meat is tender and falling off the bone.

5-Next, remove lamb from the sauce, shred the meat, and mix back into the mushroom gravy with any additional ingredients like heavy cream if desired.

6-Finally, preheat oven to 400°F (200°C) and spoon the filling into individual ramekins or a larger pie dish.

7-Then, cover the filling with puff pastry or pie crust, sealing edges and cutting vents for steam to escape, then bake for 25-30 minutes until the crust is golden and puffed.