Heat a wide sauté pan with oil. Place the beef slices in the pan and sear until browned on each side, about 2 minutes per side. Remove the meat to a plate and set aside until the sauce is ready.

In the same pan with the meat drippings, sauté the sliced onions until browned. Add the leek and stir for a few minutes. Add the mushrooms and continue stirring for a few more minutes. Add the spices and stir to combine. Add 1/2 liter (2 cups) of water and bring to a boil.

Return the seared beef slices to the pan and cover with a lid. Cook on medium heat for about 30 minutes.

Heat another pan with oil (deep enough for frying). Fry the potatoes until golden brown and remove to a plate lined with paper towels.

Add the fried potatoes to the pan with the meat and sauce. If needed, add more water to the pan. Continue cooking on low heat for an additional 1 hour and 15 minutes, or until a fork easily pierces the roast and it is tender.