Directions:
1. Preheat the oven to 450 degree F. In a small bowl whisk olive oil and mustard well. Apply two tablespoons of this mustard mixture on the steak. Sprinkle black pepper on it and set aside. Into the remaining mixture, add two tablespoons of cold water, tarragon and chives and whisk them well.
2. Cut the potatoes into quarter inch thick sticks and pat them dry. In a large bowl whisk together a quarter teaspoon of salt, cayenne pepper, paprika and the egg whites. Add the tomatoes to this mixture and toss. Apply the cooking spray on the rimmed baking sheet. After letting the excess of the egg mixture drip off it, spread the potatoes on the tray and spray the cooking spray on top. Bake them for around 25 minutes till they turn golden brown.
3. In the meanwhile take a large cast iron skillet and sprinkle quarter of a teaspoon of salt on it. Heat this over high flame until it becomes very hot. Add the steaks to the skillet and keep another heavy skillet on top to weigh down the steak. After it is seared for around 3 minutes per side till it turns brown, turn off the flame and let the steak rest in the pan for 5 to 8 minutes for it to be cooked medium rare. Slice the steak into thin pieces and serve them with the potato fries and herb mustard.