Start by boiling water in a large pot. Once it’s bubbling like a cauldron, add the egg noodles. Cook according to the package instructions until they’re al dente. This gives the noodles the perfect chew. Once done, drain them and set aside.

In a large skillet, melt one tablespoon of butter over medium heat. Add the diced onions and celery. Sauté until they are soft and fragrant—about 5 minutes. Stir occasionally to avoid burning.

In a large mixing bowl, combine the sautéed vegetables, drained tuna, thawed peas, the cream of mushroom soup, whole milk, chopped parsley, and Dijon mustard. Stir everything together until it's fully integrated.

Now, fold the cooked noodles into the mixture. Gently stir until the noodles are thoroughly coated with the tuna and sauce. Make sure the tuna is broken up into smaller pieces for even distribution.

In a separate bowl, mix the panko bread crumbs, chopped parsley, shredded cheddar cheese, melted butter, and smoked paprika. This delicious topping will add that satisfying crunch everyone loves.

Preheat your oven to 350°F (175°C). Transfer the tuna mixture into a greased casserole dish. Evenly spread the breadcrumb mixture over the top. Bake for around 25-30 minutes until the casserole is bubbly and the topping is golden brown.

Once it's done, let it sit for about 5 minutes. This allows the flavors to mingle. Dish it out, and watch everyone’s eyes light up!