Melt butter and oil over high heat. Pat meat dry and brown meat on all sides; remove to a plate and cover to keep warm.

If using mushrooms, add them to the same skillet and cook until they are beginning to brown; remove them to the plate with the meat so they stay warm.

In the same skillet, add the onion and cook for about a minute to soften. Deglaze the pan with the wine, letting it reduce a bit--maybe 25%. Then add the cream and cook until slightly thickened.

Add the meat, the sautéed potatoes and mushrooms (if using) back to the pan. Stir to combine and heat through.