Combine oil, garlic and rosemary in a small shallow baking dish. Add the beef and toss to coat. Cover and refrigerate for at least 2 hours or overnight. Let sit out at room temperature for 30 minutes before grilling. Preheat grill. Remove beef from marinade, season with salt and pepper to taste and grill for 4 to 5 minutes on each side for medium rare doneness. Let rest 10 minutes then cut into dice.
Squeeze the lemons into a measuring cup to measure 1/4 cup. Place the juice in a blender with the shallot, rosemary and garlic and blend until smooth. With the motor running, slowly add the olive oil until emulsified and season with salt and pepper to taste.
Place the romaine in a large bowl and toss with 1/4 cup of the lemon vinaigrette and season with salt and pepper to taste. Arrange the dressed lettuce in the center of each plate. Arrange some of the prosciutto in a vertical line along the far-left side of the greens. Next to that arrange the scallions, then red tomatoes, then yellow tomatoes, then Gorgonzola, then hard cooked eggs, then avocado. Drizzle with a little more of the lemon vinaigrette and garnish with chopped chives.
Recipe Copyright 1999 by Bobby Flay. All Rights Reserved