Dice the onion, peel the carrot, and cut it into slices, chop the celery into slices, and mince the garlic.
1 medium onion, 1 large carrot, 1 celery stalk, 3 cloves garlic
Heat the oil in a large pot (preferably a Dutch oven or thick-bottomed pot with a tight-fitting lid) over high heat.
2 tablespoon frying oil
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.
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.
1 teaspoon tomato paste
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.
1 cup dry red wine
Add beef broth and bring to a boil.
2 cups good-quality beef broth
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.
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).
When the Rouladen are done, transfer them to a plate.
Strain the sauce. You can discard the vegetables or serve them with dinner.
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.
2 tablespoons corn starch
Remove toothpicks or kitchen twine from the Rouladen.
Put the Rouladen back in the pot and cook briefly in the gravy until heated through. Serve.
Enjoy!