There’s lots of yummy toppings you can use: Panko bread crumbs, crushed potato chips, crushed crackers or crispy fried onions. You can prepare this casserole in advance. But when baking the next day, add extra time because the whole casserole is cold. For the tuna, we found a big flavor and texture difference by using the solid white chunk albacore tuna vs the chunk light style tunas. Feel free to use more or less tuna depending on your personal taste preference.
Preheat oven to 400°F. Lightly oil or butter a 9x13 pan.
Cook the pasta: Cook egg noodles according to package instructions. Drain and pour into the prepared 9x13 pan.
Make the crumb topping: In bowl combine 1 cup breadcrumbs, 3 Tablespoons melted butter and 1/2 cup parmesan cheese. Set aside.
Make the filling: Heat large skillet on medium-high heat. Add 2 Tablespoons oil and cook onions and celery until softened. Add peas/carrots, garlic and 2 cups chicken broth. Stir and bring mixture to a simmer.
Whisk 1/4 cup flour into the 1 cup of milk, then add the whisked mixture into the simmering pan with the veggies and broth. Stirring regularly, cook until mixture thickens, then add 12 oz. tuna, 1/2 teaspoon salt and 1/2 teaspoon pepper. Remove from heat and taste the mixture. Add more salt/pepper if needed.
Pour the tuna mixture into the pasta pan and stir in the 2 cups grated cheese.
Top the pan with the breadcrumb mixture.
Bake at 400°F for about 20-25 minutes or until bubbly and crispy brown. Serve warm.