Crunchy Tuna Casserole

Preheat oven to 375 degrees F. In a large pot of boiling salted water, cook pasta according to package directions until al dente. Drain and set aside. Meanwhile, in a medium pot over medium heat, melt 2 tablespoons butter and cook onion until translucent, 2 to 3 minutes. Add 2 tablespoons reserved oil from tuna, flour, 1 teaspoon salt, and 1/2 teaspoon black pepper and stir until flour turns golden, about 3 minutes. Add wine and stir until smooth, then add chicken stock and continuously stir until incorporated. Bring to a boil, then reduce to a simmer until sauce begins to thicken, 5 minutes. Add cooked pasta, frozen peas, tomato, 1 cup mozzarella, Parmesan, and tuna. In a small bowl, stir together panko, olive oil, and parsley. In a large baking dish, layer pasta mixture and top with remaining cup of mozzarella and breadcrumb mixture. Season generously with salt and pepper. Bake until golden and bubbling, 20 minutes. Serve with parsley.