For marinade, combine mustard, oil, rosemary, shallots and garlic. Rub on lamb chops, cover and let marinate 8 hours or overnight. Remove chops from marinade and discard marinade. Season the lamb chops with salt and pepper.
Brush grill rack with olive oil. Grill lamb over coals covered with grey ash 4 to 5 inches from coals. Grill for 6 to 10 minutes per side to desired degree of doneness: 145°F for medium-rare, 160°F for medium or 170°F for well. Transfer lamb chops to platter, cover and let stand 5 minutes.
Bring a medium saucepan of water to a boil. Make a small x on the bottom of each tomato. Core the tomatoes and pierce with a fork. Plunge in boiling water for about 30 seconds to loosen skin. Transfer tomatoes to a strainer. When cool enough to handle, peel off skins. Cut tomatoes in half horizontally. Place the strainer over a bowl; scoop the seeds and pulp from tomatoes into strainer. Press pulp to extract as much juice as possible, set aside.
On plate, arrange tomato halves, cut-side up. Sprinkle with garlic and season with salt and pepper. Drizzle with 2 tablespoons olive oil. Allow to stand for 30 minutes.
Brush baguette slices with remaining oil. Grill or broil 1 to 2 minutes per side until golden brown. Grill or broil tomatoes on cut side until lightly charred, about 4 to 5 minutes.
Lightly oil a 13 by 9-inch baking dish. Arrange half of the tomatoes in dish cut-side up, pressing them down with a spatula. Sprinkle tomatoes with 2 tablespoons each parsley and basil. Lightly season tomatoes with salt and pepper. Top the tomatoes with half of the baguette slices. Repeat process. Pour reserved tomato juice (about 1 cup) evenly over the bread pudding. Cover with foil and weigh with another pan. Bake in 350°F oven for 45 minutes or until liquid is absorbed.
Remove weighted pan and foil. Increase oven temperature to 375°F and bake additional 10 to 15 minutes until top of bread is lightly browned. Remove from oven and sprinkle with remaining 1 tablespoon each of parsley and basil. Let stand for 15 minutes.
To serve: Place lamb rack chops on each plate and garnish with parsley sprigs. Serve with a slice of tomato-bread pudding.