Preheat oven to 400°F.
Cook penne al dente in a large pot of salted water in a large stockpot according to package instructions. Drain and set aside.
Meanwhile, as the water for the noodles is cooking, heat butter olive oil in a large saute pan over medium-high heat. Add onion and carrots, and saute for 5-7 minutes, or until both are soft. Add garlic and saute for 1 more minute until fragrant. Stir in the flour and cook for 1 more minute. Whisk in the chicken stock until it is combined, then stir in the milk, Italian seasoning, salt, pepper, mushrooms, peas and tuna. Continue cooking, stirring occasionally, until the mixture reaches a simmer and thickens and the mushrooms are cooked, about 4-6 more minutes.
Once the noodles are ready, add the sauce mixture to the (drained) noodles, and toss to combine. Stir in the cheddar cheese until it is evenly combined.
If you are baking the casserole, pour the noodles into a greased 9 x 13-inch baking pan. Sprinkle the Panko breadcrumbs evenly on top of the pasta, then drizzle a bit more Butter Olive Oil on top. Bake for 18-20 minutes, or until the top of the pasta is slightly crispy and golden, and the filling is bubbly on the sides.
Prep: 10 minutes
Cook: 30 minutes
Makes: 4 servings