Prepare the campfire with a sturdy grate or a grill for cooking. You'll need a strong, stable fire with a consistent heat source.
Heat 2 tbsp of butter in Dutch Oven. Add 1/2 the mushrooms. Sprinkle with salt and cook until slightly browned. Add wine and cook until the wine is completely absorbed. Remove from pot and set aside. Repeat the process for the second batch of mushrooms and also set aside.
Heat second 2 tbsps of butter in Dutch Oven. Add the leeks, season with salt, and cook until tender, about 3 minutes. Add in potatoes and the mushrooms. Sprinkle mixture with flour and stir until vegetables are evenly coated. Add pheasant, thyme, chicken broth, and cream. Bring to a simmer and cook for 15 - 20 minutes over the coldest part of the fire.
While the filling is simmering, roll out the pastry and cut it into circles or squares that are large enough to cover the campfire pot.
Remove the Dutch Oven from the fire. Place the puff pastry circles or squares on top of the filling, covering completely. Brush with egg wash. Cover with lid and add embers to lid. Bake for 15 - 20 minutes or until the puff pastry is golden brown and puffed up, and the filling is hot and bubbly.
Carefully remove the skillet from the campfire. Allow to cool for 5-10 minutes before serving. Garnish with fresh thyme.
