For the sauce, heat the olive oil in a medium saucepan over medium-high heat, and saute the shallot until it becomes translucent. Add the mushrooms and cook until they are tender and give up their juices. (While the mushrooms are cooling, begin sauteing the bacon in a separate skillet for the potatoes.) Add the merlot and cook for about 5 minutes. Meanwhile, in a separate small bowl, make a slurry with 1 tablespoon water and the cornstarch, then add the tomato paste and Dijon mustard and mix thoroughly until smooth. Add this mixture to the pan of mushrooms along with demi-glace and parsley. Season with salt and pepper, to taste. Turn heat down to medium-low, and allow to reduce and thicken.
White the mushrooms are cooking, heat the oil in the deep-fryer to 375 degrees F or according the manufacturer's instructions for potatoes. Saute the bacon strips in a skillet until crispy. Remove to paper towels to drain and cool to room temperature. Drain excess bacon fat from the skillet leaving a coating in which to saute the onion. Cook until the onion becomes translucent. Deep-fry the baby potato slices until golden and drain on paper towels. Transfer them to the pan of onions, and crumble in the bacon. Toss in the scallions and season with salt and pepper. Cover and keep warm.
Heat the oven to 375 degrees F for the steak, if you are finishing in the oven. Heat olive oil over medium-high heat in a skillet with oven-safe handles. Season the steaks with salt and pepper and sear for about 2 minutes per side undisturbed (to let seasonings integrate into the surface of the meat) and then to your preferred level of doneness. Transfer the entire skillet to the oven to finish (about 10 minutes for medium- rare) They can also be cooked on a grill. Let steaks rest, then slice into 1/4-inch thick slices.
To serve spoon some potatoes, top with a "fan" of steak slices and drizzle sauce over sliced steak. Garnish the plate with haricots verts.