1. In a shallow bowl, combine the beef skirt steak, beer, lime juice, salt (optional), pepper (optional), and herbs (optional). Mix until all ingredients are evenly combined and set aside.

2. Heat oil in a large skillet over medium-high heat. Add the spring onions and cook until softened, about 5 minutes. Add the marinated beef skirt steak to the pan and cook for 5 minutes on each side or until desired doneness is reached.

3. Warm the corn tortillas in the microwave or on a griddle. Place the cooked beef on the tortillas and top with additional spring onions and a squeeze of fresh lime juice if desired.