Preheat oven to 400°F (200°C).
In a large skillet, heat olive oil over medium heat. Add diced onion and cook until soft, about 5 minutes.
Add mushrooms, thyme, and sage, and sauté for 5-7 minutes until mushrooms are golden.
Sprinkle flour over vegetables and stir to coat. Slowly pour in the turkey stock while stirring.
Bring to a simmer and cook for 5 minutes until thickened. Stir in cream, shredded turkey, peas, and season with salt and pepper.
Pour the filling into a baking dish.