In a large non stick pan heat oil over medium high heat and brown meat season with salt and pepper. Once browned drain and put aside

Melt butter in the skillet add the onions and cook until soften, then add mushrooms cook all together until mushrooms soften

Stir in beef broth, sour cream, and mustard cook until it soothes out then add meat

Reduce to low heat and cook until meat is heated all the way through season to taste with salt and pepper