1. Preheat oven to 400°F. Grease a pie pan or 2 quart baking dish. Set aside.
2. In a large skillet, heat the olive oil over medium-high heat. Stir in the onion and cook until soft, about 3 minutes.
3. Add in the garlic, mushrooms and thyme. Cook for 3 minutes. Sprinkle in the flour and cook for 3 minutes.
4. Slowly pour in the stock, whisking until well combined and thickened, about 5 minutes. Stir in the peas and turkey.
5. Transfer the mixture into the prepared pan. Spoon the potatoes to completely cover turkey filling. Sprinkle with cheese and bake until cheese has melted and potatoes are crisp, about 20 -25 minutes.