1) Slice potato into matchsticks and add to a small bowl of cold water to rinse briefly. Drain potatoes and dry them on a few paper towels. Slice veggies for the stir-fry and cut steak in to small strips. Whisk together soy sauce, tomato paste, vinegar, and cumin to make a sauce.
2) Heat about two inches of oil in a sturdy pot or wok until it registers 350 degrees Fahrenheit. Add potatoes and fry until they are golden brown, about 6-8 minutes.
3) Remove potatoes and let the fries drain on a few paper towels, then keep them warm in a 300 degree oven until needed.
4) Carefully pour out oil in the wok. Add beef and stir-fry for a few minutes over medium-high heat until it is just cooked through which should just take a few minutes.
5) Remove beef and add veggies to the wok. Cook for a few minutes until they are cooked through, but still a bit crispy. Add beer to pan and use the liquid to scrape up any bits.
6) Stir in sauce and let thicken for a minute. Then add beef to reheat.
7) Serve stir-fry over rice with fresh cilantro and potatoes on the side.