Prepare all ingredients: cut chicken, slice mushrooms, chop onion, and mince garlic. Preheat oven to 200°C (390°F).
Heat olive oil and butter in a skillet, then sauté onion and garlic until translucent. Add chicken pieces, cooking until golden brown. Incorporate mushrooms and continue cooking for an additional 5 minutes.
Add flour over the mixture and stir. Slowly incorporate chicken stock and cream, whisking into a smooth sauce. Season with salt, pepper, and thyme, allowing it to thicken.
Place one pie crust in the baking dish, pour the filling, cover with second crust, and seal edges. Make cuts for steam release and brush with egg wash.
Bake the pie in the preheated oven for 40–45 minutes until golden brown. Let it cool slightly before serving.
Notes
Ensure leftovers are kept in airtight containers to maintain freshness. Reheat gently in the oven for the best texture.