Heat the butter in a large skillet over medium-high heat. Add butter and the mushrooms and cook, stirring occasionally, until they start to brown about 5 minutes.
Reduce the heat to medium and add the red wine, beef stock, pepper, garlic, and onions. Simmer uncovered for 15 minutes, stirring occasionally.
Add salt to taste, and transfer the mushroom.
Make sure to sauté until all the liquid has almost evaporated. Then stir for another 5 minutes.
Serve with your favorite steak or pasta.