Preheat your oven to 400°F (200°C).
Take the steaks out of the refrigerator and let them sit at room temperature for about 30 minutes to take the chill off.
Pat the steaks dry with paper towels to remove any excess moisture. Season them generously on both sides with salt and pepper.
Heat a cast iron skillet or oven-safe skillet over medium-high heat on the stovetop. Add a drizzle of oil to the skillet and swirl to coat the bottom.
Once the skillet is hot, carefully place the steaks in the skillet. Sear the steaks for about 2-3 minutes on each side until they develop a golden-brown crust.
If desired, add a tablespoon of butter to the skillet along with minced garlic and fresh herbs. Spoon the melted butter over the steaks as they cook to add flavor.
Once the steaks are seared on both sides, transfer the skillet to the preheated oven. Cook the steaks in the oven for about 5-10 minutes, depending on desired doneness and thickness of the steaks:
**For rare**: Cook for about 5 minutes. **For medium-rare**: Cook for about 7 minutes.**For medium**: Cook for about 9 minutes.**For well-done**: Cook for about 10 minutes or longer. Use an instant-read meat thermometer to check the internal temperature of the steaks. For medium-rare, the temperature should register around 130-135°F (54-57°C).
While the steak is finishing, preheat the frying oil to 375 F in a large pot. You can test one French fry to make sure it is the right temp if you don’t have a thermometer. The oil should strongly bubble once the fry hits the oil and it should be completely fried and golden within a few minutes.
Once the steaks reach the desired doneness, remove the skillet from the oven and transfer the steaks to a cutting board. Let them rest for 10 minutes.
For the sauce, add the shallot and pepper and sauté. Deglaze the pan withcognac and scrape up any browned bits. Let that cook for 2-3 minutes, then add the demi glaze paste, water and Worcestershire sauce. Stir together until smooth. Let it come to a bubble and thicken. Finally, add the heavy cream and stir. Let it bubble for 1-2 min until thick.
You’re going to play a little game of multi task during the simmering stages of the sauce and use that time to fry the French fries. Submerge them into the oil and fry until golden brown and crispy. Remove and place on a rack or in a metal bowl and season with a generous pinch of salt.
Slice the steaks against the grain and serve immediately as instructed above.