Sprinkle salt on both sides of the steak and set aside, at room temperature, for 15 - 30 minutes.
In a small bowl, whisk together broth, Worcestershire sauce, Dijon mustard and tomato paste; set aside.
In a skillet, over medium-high heat, melt the butter.
Pat the steaks dry with a paper towel.
Increase the heat to high and sear the meat for 1 - 4 minutes, depending on how thick the steak is; you may need to cook the meat in batches.
Turn and sear on the other side; use the finger test to check the doneness of the meat; when the steaks are done, move to a cutting board and tent with foil. While the meat is resting, sauté the shallots in the pan, 2 minutes on medium-high heat, stirring once or twice.
Add the cognac to deglaze the pan; increase the heat and cook until the cognac is almost evaporated.
Stir in the broth mixture and bring to a boil; cook until thickened, about 2 - 3 minutes.
Stir in the cream and cook for two more minutes.
If you want, thinly slice the steak to serve; otherwise serve individual steaks.
Drizzle warm Diane sauce over the steak and garnish with freshly ground black pepper and chives.