To prepare the roasted tomatoes:
Position the rack in the center of the oven and preheat the oven to 500°F. Place the tomatoes on a baking sheet. Arrange the garlic slices on top of the tomatoes and scatter the thyme sprigs over the tomatoes. Drizzle with the oil and sprinkle with salt and pepper. Roast until the tomatoes are tender and golden brown on the bottom, about 20 minutes. Set aside.
To prepare the burgers:
Heat 1 tablespoon of oil in a heavy large sauté pan over medium heat. Working in batches, lay the prosciutto slices in the pan and cook over medium heat until crisp and golden, about 2 minutes per side. Transfer the crisped prosciutto to a paper towel-lined plate.
Heat the remaining 1 tablespoon of oil in a heavy small sauté pan over medium heat. Add the shallots. Sprinkle with salt and pepper and sauté until tender, about 2 minutes. Stir in the minced garlic. Remove from the heat and cool completely.
Gently mix the cooled sautéed shallots and garlic with the ground beef, parsley, mustard, Worcestershire sauce, 1/2 teaspoon of salt, and 1/4 teaspoon of pepper in a large bowl until well blended. Mix in the egg. Divide the beef mixture into 4 equal mounds. Using a 4-inch ring mold, shape each mound into a patty.
Preheat a grill pan or prepare a barbecue for medium-high heat. Brush the cut sides of the ciabatta with butter. Grill the ciabatta, cut side down, until lightly toasted, about 2 minutes. Place the ciabatta on a plate and cover to keep warm.
Grill the patties until brown on the bottom, about 3 minutes. Turn the patties over. Top the patties with the roasted tomatoes and then with the cheese. Continue to grill until the patties are cooked to medium-rare doneness, about 3 minutes longer.
Meanwhile, to make the gourmet ketchup:
Whisk the ketchup, mustard, vinegar, Worcestershire sauce, chives, and tarragon in a large bowl to blend. Gradually whisk in the oil to blend well. Set the sauce aside.
Place the lettuce over the grilled ciabatta bottoms. Set the patties on the lettuce. Spoon some gourmet ketchup over the burgers. Top with the crisped prosciutto. Cover with the ciabatta tops. Serve the remaining gourmet ketchup alongside.
When Curtis Stone, host of Bravo's Around the World in 80 Plates and Top Chef Masters, realized he wanted to be a chef, he left Australia and headed for Europe. After traveling around a few months, he landed in London at the doorstep of Marco Pierre White.