Heat butter and olive oil in a large, deep saucepan over medium heat until melted. Sprinkle flour over the butter and whisk until smooth. Continue to cook, whisking often, until the mixture has turned a golden tan color {a blond roux}.
Stir in onion, carrot, celery and tomatoes, mushroom & garlic, and cook for about 5 minutes. The mixture will thicken and become pasty.
Add vegetable stock a little at a time while whisking to avoid lumps, then whisk in wine and add bay leaves and thyme. Add salt and pepper to taste.
Bring to a bubble and allow to simmer for about 20 minutes, stirring/scraping the bottom of the pan every so often, until the liquid has reduced and the sauce has thickened quite a bit.
Add the raw shrimp to the pan and cook for about 5 minutes, until opaque and cooked through.
Serve over {or with a scoop of} rice.