Ask your butcher to cut off crosswise 500-600 g of skirt or sirloin into thin slices. Next the slices should be divided into two or three strips. You can still ask your butcher to do it or you can can easily do it at home.
Don’t worry if the slices are not paper thin. I actually prefer them not be so thin so I can cook them for longer, which gives more flavour to the meat.
Pat dry the beef straccetti.
Heat up a tablespoon of olive oil in a wide pan (that will accommodate all the meat without overcrowding). Add the meat strips spreading them across the pan and fry on a medium heat.
Once they have turned brown on one side turn them up side down and brown them too.
Don’t worry at this stage if the meat starts releasing its juices. Just carry on cooking the meat on a low heat and stirring it. Once the juices are almost gone and the meat starts to catch to the pan pour in the white wine and wait until it almost evaporates.
Sprinkle some marjoram, give it a stir and start cooking on a low heat. Season with salt and pepper (you may need more seasoning than you think and you can always adjust it towards the end of cooking).
Check on the meat and stir every few minutes. The straccetti should be cooking in their own juices, if the meat seems dry add a bit of water.
Depending on the thickness of the sliced beef you bought, the cooking time will vary, but it shouldn’t exceed 30 minutes. It takes me 20 minutes on average.
Once the meat is soft and moist, season again to your liking and add some balsamic vinegar. Stir everything very well and keep the pan on for one more minute (always on a low heat).
Arrange the rucola leaves on a serving plate. Spread the straccetti on top and garnish with shaved parmesan. Drizzle more balsamic over the dish if you wish. Serve immediately.