Combine the beef in water with the salt, bay leaves and two cloves of garlic. Bring to a quick boil, cover and then simmer for 1.5 hours or until tender. Be sure the beef is covered by water while cooking.
Remove meat from the water, reserving the broth and garlic, allowing the meat to cool slightly on a cutting board. Discard the bay leaves.
Cut the steak in half lengthwise and then using two forks (or your fingers) shred each half into small “threads” about three inches long.
Combine the sliced tomatoes, onion, reserved garlic, red bell pepper, chile guaque and three cups of broth in a saucepan
Bring to a boil, reduce heat and simmer for 10 minutes.
Transfer tomato mixture to a food processor or blender. Blend until a smooth consistency is reached. You may need to do this in batches.
Add vegetable oil to a Dutch oven (or large saucepan) and heat to medium high.
Strain the tomato puree into the vegetable oil, bring to a boil and simmer for 10 minutes with two sprigs of thyme until slightly thickened. If sauce is too thick, add more broth or if too thin, add a puree of toasted tortilla (or French bread) and broth.
While the sauce is simmering, peel and slice the potatoes into pieces two inches long and ½ inch thick. Parboil separately in water until soft but still firm.
When the sauce has thickened, remove the sprigs of thyme, add the parboiled potatoes and shredded beef.
Simmer for 10 minutes until potatoes are tender and sauce is thickened. Add fresh ground pepper and adjust salt to taste.
Garnish with sprigs of thyme and serve immediately in bowls or on a plate with a mound of white rice, slice of avocado and fresh corn tortilla.