Chicken and Ham Stuffed Shells

Heat oven to 400 degrees F. Cook 16 jumbo shells according to package directions. Drain and rinse under cold water to cool. Spread all but 1/2 cup of the béchamel sauce on the bottom of a large broiler-proof baking dish. In a large bowl, whisk together the 1/2 cup béchamel with the Dijon mustard and Worcestershire sauce. Toss with shredded rotisserie chicken. Fold in grated Gruyère cheese, thinly sliced deli ham, small red onion, fresh tarragon, and pepper. Spoon the mixture into the shells (about 1/4 cup each) and place on top of the sauce. In a bowl, combine panko bread crumbs and olive oil. Sprinkle over the shells, cover with foil, and bake until the shells are heated through, 12 to 15 minutes. Heat broiler. Uncover, and broil until the cheese begins to brown, 2 to 3 minutes.