Rouladen (German Beef Rolls)

Make the Rouladen:

1. Place the meat slices on a wooden board, cover with plastic wrap, and pound with a meat mallet until a little bit thinner than 1/4 inch (6mm) to create long and thin strips of meat. While flattening the meat be gentle to not make any holes in the meat.
2. Season the meat with salt and pepper on both sides. Spread a thin layer of mustard on one side of the meat and place 1-2 slices of bacon on top (as much as will fit in a single layer, if you can fit 2 slices of bacon side by side - use two pieces or cut them to fit).
3. Place 1-2 pickles (cut thicker ones in half lengthwise or 4 parts) and 1-2 tablespoons of diced onions on top of the bacon.
4. Roll up the meat and secure it with toothpicks or kitchen twine. The rolls don´t need to be rolled very tightly, just enough for the meat to keep its rolled shape (if the mustard is leaking out, it will just flavor the gravy, it´s fine).
5. Repeat with the remaining ingredients.

Cook Rouladen:

1. Dice the onion, peel the carrot, and cut it into slices, chop the celery into slices, and mince the garlic.
2. Heat the oil in a large pot (preferably a Dutch oven or thick-bottomed pot with a tight-fitting lid) over high heat.
3. When hot, cook the Rouladen in batches until well-browned on all sides (shouldn´t be overcrowded or won´t brown properly). Transfer to a plate.
4. Reduce the heat to medium-low and add the carrots, onions, and celery. Cook for a couple of minutes until softened. Add the garlic and tomato paste, cook for 30 seconds.
5. Add the wine and cook until reduced at least in half. Scrape all the brown bits at the bottom of the pot - they will give lots of flavor to the gravy.
6. Add beef broth and bring to a boil.
7. Add Rouladen back to the pot, cover the pot, and cook over low heat (the sauce should only simmer) until the beef is very tender, about 1 1/2 hours. Turn the Rouladen halfway through the cooking time and pour them a couple of times with the sauce.
8. The cooking time will depend on the thickness and cut of the meat so you may need to check if your Rouladen are done a little bit sooner or need a longer cooking time (for up to 2 hours).
9. When the Rouladen are done, transfer them to a plate.
10. Strain the sauce. You can discard the vegetables or serve them with dinner.
11. In a small bowl, combine 2 tablespoons of cornstarch and 3 tablespoons of cold water. Add to the sauce, bring to a boil, and cook for a couple minutes or until the sauce is thickened. Check if the sauce needs more salt and pepper (it shouldn´t, but it´s better to check). If it´s too salty, you can add more beef broth (preferably unsalted) or a small amount of water.
12. Remove toothpicks or kitchen twine from the Rouladen.
13. Put the Rouladen back in the pot and cook briefly in the gravy until heated through. Serve.
14. Enjoy!