Reduce the heat to medium. Add the butter to the still hot skillet, and allow it to melt.
1 tbsp butter
Add the minced shallot to the melted butter.
1 small shallot
Sauté the shallot in the melted butter until soft.
Add the cognac to the center of the pan.
1/4 cup cognac or brandy
Use your spatula to scrape up the pan drippings (fond) from the pan while the cognac reduces.
Allow the cognac to reduce by half.
Add the beef stock, and incorporate it into the sauce. Allow the sauce to reduce by half again.
1/2 cup beef stock
Add the heavy cream to the sauce, and stir it in until fully incorporated.
1/3 cup heavy cream
Add the minced parsley and chives to the sauce.
1 tbsp fresh parsley, 1 tbsp fresh chives
Add the Dijon mustard and Worcestershire to the sauce.
1 tsp Dijon mustard, 2 dashes Worcestershire sauce
Allow the sauce to reduce to a thick consistency. Add the salt and pepper to taste.
1 pinch kosher salt, 1 pinch black pepper
Carve the steak across the grain into ½ inch slices. Serve with a ladle of sauce poured over the top of the steak.