Heat a large, heavy skillet (I use cast iron) over medium high heat. Add 1 TBL olive oil. Season steaks with salt and pepper and saute in pan for 5 minutes on each side for medium rare (less time for rare and more for medium). Remove steaks from pan and allow to rest while you make the sauce.
Return the pan to medium high heat and add 2 TBL butter until melted. Add 1/2 cup chopped shallots (mushrooms if using) and cook for 3 minutes until softened. Stir in:
1/4 cup beef stock
1/4 cup brandy or white wine
1 TBL dijon mustard
2 tsp fresh lemon juice
1 tsp Worcestershire sauce
1 cup sliced mushrooms *optional*
Boil for 2 minutes, scraping the bottom of the pan to incorporate all of that steaky goodness into the sauce. Add any juices that have accumulated on the steak platter.
Remove the pan from the heat and stir in 1-2 TBL cream or half and half.
Pour sauce over steaks and garnish with some chopped parsley.
Enjoy with some potatoes, asparagus, and a nice glass of red.