Instructions

• In a small saucepan over high heat on the stove, bring the balsamic vinegar to a boil. Boil until reduced to 3 tablespoons, 3 to 4 minutes, stirring occasionally. Remove the saucepan from the heat and stir in 2½ teaspoons of the brown sugar. Stir in the butter and cook until melted. Season with a pinch of salt and pepper. (If a sweeter glaze is desired, stir in the remaining ½ teaspoon brown sugar.) 
• Prepare the grill for direct cooking over high heat (500° to 550°F). 
  Prepare the grill for cooking over high heat (550°F). 
• Allow the steaks to stand at room temperature for 15 to 30 minutes before grilling. 
• Remove and discard the thick center ribs from the chard. Cut the leaves lengthwise in half and then crosswise into ¾- to 1-inch strips.
• In a large skillet over medium-high heat on the stove, warm 2 tablespoons of the oil. Add the onion and sauté until it begins to soften, 5 to 6 minutes. Add the garlic and cook for 30 seconds, stirring constantly. Stir in the chard by large handfuls and toss with tongs until wilted and almost tender but still bright green, 4 to 5 minutes. Stir in the currants and olives and sauté for 2 minutes more. Season with ¼ teaspoon pepper and salt, if desired (the olives may provide enough salt). Stir in the pine nuts. Keep warm.
• Brush the cooking grates clean. Pat the steaks dry with paper towels. Brush the steaks on both sides with the remaining 2 tablespoons oil. Season evenly with ¾ teaspoon salt and ¾ teaspoon pepper. Grill the steaks over direct high heat, with the lid closed, until cooked to your desired doneness, 6 to 8 minutes for medium rare, turning once or twice. Remove from the grill and let rest for 3 to 5 minutes.
  Brush the cooking grates clean. Pat the steaks dry with paper towels. Brush the steaks on both sides with the remaining 2 tablespoons oil. Season evenly with ¾ teaspoon salt and ¾ teaspoon pepper. Grill the steaks over high heat, with the lid closed, until cooked to your desired doneness, 6 to 8 minutes for medium rare, turning once or twice. Remove from the grill and let rest for 3 to 5 minutes.
• Cut the steaks across the grain into slices. Reheat the balsamic glaze, if necessary. Serve the steaks warm with the chard and the balsamic glaze drizzled over the steak slices.