Preheat your oven to 180°C (350°F). In a large pot, bring salted water to a boil and cook the egg noodles just until al dente, about 6 minutes. Drain and set aside. Avoid overcooking, as they’ll continue softening in the oven.

In a saucepan over medium heat, melt the butter and sauté the chopped onion for 3 to 4 minutes until soft and translucent. Add the minced garlic and cook for another 30 seconds. This builds the casserole’s base flavour.

Reduce the heat to low and stir in the cream of mushroom soup and milk. Whisk gently until the mixture is smooth and heated through. Season with salt and pepper, adjusting to your taste.

Add the drained tuna and frozen peas into the sauce. Stir gently to combine without breaking the tuna too much. Let it warm through for 2 minutes, just until the peas begin to soften.

In a large mixing bowl, combine the cooked noodles with the tuna and sauce mixture. Add the shredded cheddar and gently fold until everything is evenly coated. This helps the flavours meld beautifully.

Lightly grease a medium sized baking dish (about 20x20cm). Spoon the tuna noodle mixture into the dish and spread it out evenly with a spatula.

In a small bowl, mix the crushed crackers or breadcrumbs with melted butter and optional Parmesan. Sprinkle this mixture over the casserole for a crunchy golden topping.

Place the dish on the middle oven rack and bake uncovered for 25 to 30 minutes, or until bubbling around the edges and the topping is crisp and golden.

Remove the casserole from the oven and let it rest for 5 to 10 minutes. This allows the sauce to thicken slightly, making for cleaner servings and better flavour.

Serve warm, garnished with chopped parsley if desired. Tuna casserole pairs well with a green salad or buttered green beans for balance. A dash of hot sauce or a lemon wedge on the side can brighten the dish.