Preheat broiler.
Place a large pot of water over high heat to boil the pasta and a medium pot of water over high heat for the beans. When they come to a boil, salt them both. Drop the pasta into one, cook to al dente according to package directions, then drain and reserve in the pot it was cooked in. Drop the beans in the other pot and cook until bright green and tender, about 3 minutes, then drain the beans and reserve.
While the pasta and beans are cooking, place a large skillet over medium heat with 4 turns of the pan of EVOO, about 1/4 cup. Add the anchovies to the pan and cook until they've melted into the oil, about 2 minutes. Add the shallots and garlic to the pan, and cook until tender, 2-3 minutes.
Add the flour, cook for about a minute, then add the wine to the pan and let it reduce by half. Stir in the cream, stock and season with salt and pepper. Bring the liquids up to a bubble and reduce until thickened, about 5 minutes. Stir the tuna and reserved green beans into the sauce and cook until heated through, about 1 minute.
To the pot with the reserved pasta, add the tuna and sauce, the Parmigiano Reggiano and olives, and toss to combine. Transfer to a casserole dish and reserve.
For the topping, melt the butter in a small skillet and remove from heat to cool. Add the toasted bread to the bowl of a food processor and pulse to chop it up into large bread crumbs. Add the breadcrumbs, parsley and Gruyere to the pan with the melted butter and toss to combine. Top the casserole with the breadcrumb-cheese mixture and pop it under the broiler until golden brown. Serve with a green salad with chopped hard-boiled egg and capers dressed with a Dijon vinaigrette alongside.