Steps

1. melt the butter and sauté the mushrooms, season with salt and pepper
2. sauté until water is gone and the mushrooms are browned a bit
3. add the flour and cook 5 min
4. add the stock, bring to a simmer and cook for 30 min

Steps

1. Heat 2 tablespoons olive oil in a large skillet over medium heat; add mushrooms, onion, and garlic to the hot oil and season with salt, black pepper, and oregano. Cook and stir mushroom mixture until mushrooms have given up their juice and the juice has almost evaporated, about 10 minutes. Transfer cooked mushrooms to a cutting board and chop into small chunks with a knife.
2. Transfer mushrooms to a large bowl. Mix in rolled oats and bread crumbs; taste for salt and black pepper and add more to taste. Stir Parmigiano-Reggiano cheese into the mixture, followed by eggs. Let mixture stand for the crumbs to soak up excess liquid, about 15 minutes. (At this point you can refrigerate the mixture to cook later if desired.) Moisten hands with a little vegetable oil or water, pick up about 1/4 cup of mixture, and form into burgers.
3. Heat remaining 2 tablespoons olive oil in a skillet over medium heat and pan-fry burgers until browned and cooked through, 5 to 6 minutes.

Steps

1. Parboil the potatoes in boiling salted water for 8-10 minutes or until just tender. Drain the potatoes and set aside.
2. Using a rolling pin, roll out the steaks to flatten and cut off the rind of fat. Season the steaks on both sides with salt and pepper (watch the step-by-step video from Gordon on how to prepare the steak).
3. Heat a little olive oil in a heavy based pan large enough to accommodate the 4 steaks in one layer. Quickly sauté the steaks on both sides for approx 1 minute to colour, then remove from the pan and set aside to rest. Drain the excess oil from the pan.
4. For the potatoes, take a clean pan and heat with olive oil. Place the potatoes in cut-side down and season with salt and pepper. Leaving their skins on, lightly crush the garlic cloves and add with the sprigs of rosemary. Once the potatoes have begun to colour toss through 30g of the butter and cook for a further 1 -2 minutes (watch the step-by-step video from Gordon on how to make sautéed potatoes).
5. To make the sauce for the steaks, heat some olive oil in the same pan used for the steaks. Slice the shallots and add to the pan, allow to soften briefly before slicing and adding the mushrooms with a little butter. Crush in the garlic and stir through. Add the Worcestershire sauce, then the mustard and heat through for a minute. Turn up the heat and tilt the pan away from you. Pour the brandy into the far end and allow it to ignite - be careful that the flame that flares up doesn't singe your eyebrows! Once the alcohol has burnt off, swirl the juices around the pan. Add the cream and allow the sauce to thicken before turning down the heat (watch the step-by-step video from Gordon on how to make the sauce for steak Diane).
6. Put the steaks back into the pan and cook a little further depending on how well done you would like them. Add half the parsley to the pan.
7. Cook the peas in a small pot with the remaining 10g butter for approximately 1 -2 minutes until tender. Season to taste with salt and pepper.
8. To serve, transfer the steaks to serving plates and spoon the sauce on top. Arrange the sautéed potatoes and peas alongside and garnish the steaks with the remaining parsley.