In a large pot, heat the oil on high for 30 seconds. Add the beef cubes and bay leaves. Sauté until golden brown. Pour in the stock and reduce the heat. Add the onions, carrots, celery, and garlic. Simmer on low for 2 hours, or until the meat is meltingly tender, making sure the soup never boils. Add the beets and cabbage during the last half hour of cooking. Spoon in the tomato paste and sprinkle with lemon juice. Add a little hot water if the soup is too thick. Stir in the dill and parsley. Season with salt and pepper. Garnish with a dollop of sour cream, if desired. Vera's Tips: For a bolder taste, substitute lamb. I like to use lamb rib chops or loin chops. Homemade stock is preferred for a deeper, more heartfelt flavor. Serve the borscht with lightly toasted and buttered whole wheat Portuguese ciabatta rolls.