In a large pan heat up the oil and add the mushrooms and onion and fry over a fairly high heat for approximately 5 minutes until golden, stirring occasionally.
Take mushrooms and onion out of the pan and to one side. In the same pan fry chopped turkey for 3-4 minutes till no longer pink and slightly season with salt and pepper.
Take out turkey of the pan and place to the side. Using the same pan on a low heat melt the butter and add the flour. Whisk till the mixture thickens, then pour in the stock and continue whisking until the sauce is thick, smooth and creamy. Stir in the fromage fraiche and season to taste.
Toss in the mushroom mixture and turkey and stir. Serve with rice.