Heat the oil in a large skillet over medium heat. Add the onion, carrot, celery and garlic and cook 4-5 minutes. Stir in the flour until well combined. Slowly mix in the stock, stirring constantly. Add the turkey and herbs. Bring to a simmer and cook until vegetables are tender, about 20 minutes. (Add more stock if too thick.) Add the peas and corn and season with salt and pepper. Simmer a few minutes more, until peas and corn are heated through.