Wash and dry the beef, rub it well with salt and black pepper on all sides and place the steaks to fry evenly in heated butter and oil. You can bake them on a grill pan. As soon as they are ready, take them out, and pour in wine to the pan to deglaze it.
In a separate container, heat a little oil and fry the tarragon sprigs, thyme and ground garlic. Then add the chopped onions. Once it is caramelized, add the flour, stir and add the slightly pre-mashed blueberries. Stir and leave it to cook.
Add some strained wine if you wish, the Worcester sauce and all the other spices. Once the sauce is reduced, it is ready. Serve the steaks drenched in the wine sauce with blueberries.