Season the hanger steak with salt and pepper, then coat in the dried porcini powder. Preheat your oven to 400 degrees. Sear in a hot pan with oil, or grill on high, for two to three minutes until the exterior is golden brown. Transfer to oven for six to seven minutes for medium rare. Remove from oven then transfer steak to a cutting board to rest. Deglaze with the red wine and reduce by half. Swirl in the butter to emulsify and make a nice pan sauce.
In a separate pot, render the pancetta over medium low heat. Add the onions and mushrooms and cook in the same pot with the pancetta fat. Cook on medium for three to four minutes, then add the beef stock and white beans. Reduce for four to five minutes until everything is evenly coated. Finish with parsley and fresh tarragon.
To serve, place some of the white bean and pancetta mix on the bottom of each plate. Slice the hanger steak and spoon on some of the red wine sauce to finish.