For the Flank Steak:
Season both sides of the flank steak with salt and pepper. Place in a large plastic sealable bag and set aside. In a mixing bowl, combine the onions, garlic, cilantro, chilies, olive oil and vinegar. Season with salt and pepper. Whisk well. Pour the marinade over the meat and seal the bag completely. Shake the bag several times to distribute the marinade. Place in the refrigerator and marinate overnight. Remove from the bag, discarding the marinade and bring to room temperature.
Preheat the grill.
Preheat the oven to 400ºF.
For the cabbage:
In a large saucepan, over medium heat, melt the butter. Add the onions. Season with salt and pepper. Sauté until wilted, about 4 to 6 minutes. Add the shallots and garlic. Season with salt and pepper. Sauté for 1 minute. Add the water and bring to a boil. Add the swamp cabbage. Season with salt and pepper. Reduce the heat to medium low and simmer until the cabbages are tender, about 1 hour. Remove from the heat and stir in the fresh herbs. Season with salt and pepper. Keep warm.
For the potatoes:
In a large mixing bowl, toss the potatoes with olive oil, salt and cracked black pepper. Place on a large baking sheet and roast until tender, about 45 minutes, shaking the pan occasionally.
Place the steak on the grill and cook for 6 to 8 minutes on each side for medium rare, moving the meat several times during cooking. Remove the steak from the grill and rest for 5 minutes. Slice the steak into individual servings. Serve with the Swamp Cabbage and Roasted Potatoes. Garnish with green onions.
Yield: 8 to 12 servings