Preheat the oven to 375°F (190°C).
In a large pan, heat olive oil over medium heat and sauté onions and garlic until softened.
Add the mushrooms and cook until tender.
Add the Arborio rice and stir to coat. Pour in white wine, cooking until absorbed.
Gradually add chicken broth, stirring frequently, and cook until the rice is tender and creamy.
Stir in the shredded chicken and Parmesan cheese, then season with salt and pepper. Let the mixture cool slightly.
Roll out the pie crust and fit it into a pie dish. Fill with the risotto mixture.
Cover with a second pie crust, crimp edges, and brush with egg wash.
Bake for 30 minutes, or until the crust is golden and crispy.
Let it cool for 10 minutes before serving.