Rub Organic Grass Fed Beef steak with the olive oil, vinegar, and 2 Tbsp chives. Set aside at room temperature for 20-30 minutes. Preheat and oil the grill. Remove steak from the marinade and season with salt and pepper to taste. Put mushrooms in the marinade and toss coat. Season with salt and pepper to taste. Grill the steak over direct medium-high heat about 6 minutes on each side for medium-rare or 8 minutes on each side for medium. Grill the mushrooms at the same time in a foil tent, on the edge of direct heat. Remove the steak and mushrooms from the grill and let rest 5 minutes. Top with remaining chives.