Preheat the oven to 180°C (350°F).
Cook the pasta in a large pot of boiling salted water according to package instructions until al dente. Drain and set aside.
While the pasta cooks, heat olive oil in a large frying pan over medium heat. Add the chopped onion and cook for 5 minutes until softened.
Add the minced garlic and cook for 1 minute more until fragrant.
Stir in the canned chopped tomatoes, dried mixed herbs, salt, and black pepper. Simmer for 5 minutes to thicken slightly.
In a separate saucepan, melt the butter over medium heat. Whisk in the flour and cook for 1-2 minutes to form a roux.
Gradually whisk in the milk, stirring continuously until the sauce thickens and is smooth.
Remove the sauce from heat and stir in 100 grams of grated cheddar cheese until melted and combined.
In a large mixing bowl, combine the cooked pasta, tomato sauce mixture, cheese sauce, flaked tuna, sweetcorn, and half of the remaining cheddar cheese. Mix gently to combine.
Transfer the mixture into a greased 9×13 inch (23×33 cm) baking dish.
Sprinkle the remaining cheddar cheese, grated Parmesan cheese, and fresh breadcrumbs evenly over the top.
Bake in the preheated oven for 25-30 minutes until the top is golden brown and bubbling.
Allow the tuna pasta bake to cool completely before covering tightly with foil or plastic wrap.
Label and freeze for up to 3 months.
To reheat from frozen, bake covered at 180°C (350°F) for 45-50 minutes until heated through, then uncover and bake for an additional 10 minutes to crisp the topping.