Season steaks on both sides with salt and pepper.

Heat a large skillet over medium to medium-high heat. Add olive oil. Once oil is shimmering, place steaks in the hot skillet. Add 2 tablespoons of the butter and cook the steaks for about 4-5 minutes on each side, or until they are nicely browned. Remove the steaks from the skillet and set aside on a plate.

Turn heat down to medium/medium-low. If skillet is scorching hot, let it cool a bit, off the heat - you don't want the butter to burn. Return skillet to heat, then add the remaining butter. Once melted, add shallots and cook for 2 minutes, stirring often. Then add garlic and cook for 1 more minute, or until shallot is translucent. If the shallot and garlic start to brown, turn down the heat or lift the skillet from the heat - you only want to soften these ingredients.

Stir in the mushrooms and cook for another 3-4 minutes, or until they are tender. If the skillet and mushrooms have a dry appearance, I add in 1-2 more tablespoons of butter.

Slowly add the cognac to the skillet and use a wooden spoon to scrape any browned bits off the bottom of the pan. Cook for about 1-2 minutes, or until the alcohol has evaporated.

Add the beef broth, Dijon mustard, and Worcestershire sauce to the skillet and bring the mixture to a boil. Reduce heat to low and simmer for 3-5 minutes, or until the sauce has thickened slightly.

Add the heavy cream to the skillet and stir to combine. Allow the sauce to simmer for 2-4 minutes to thicken. Increase the heat a bit, if needed to help with the thickening.

Bring steaks back into the skillet and let them warm through in the sauce, about 2 minutes. Serve steaks with the pan sauce immediately, over buttermilk mashed potatoes or easy creamy mashed potatoes. Garnish with fresh parsley and/or chives. Enjoy!