Open the cans of tuna, drain, and set aside.
Lightly grease a 2-quart casserole dish with 2 teaspoons of the butter and set aside.
Squeeze the potato chips inside their bag to break into small pieces. Set aside.
Make sure the oven rack is in the center position and preheat the oven to 350?F.
Bring a medium pot of water to a rolling boil over high heat. Add 1/2 teaspoon of the salt and the noodles and cook for 5 minutes, stirring occasionally with a large wooden spoon to prevent the noodles from sticking together.
Using oven mitts or pot holders, drain the noodles in a colander set in the sink, pouring away from you, and rinse under cold running water. Set aside and allow to drain well.
Melt the remaining 4 tablespoons of butter in a heavy pot over medium heat. Add the onions, celery, the remaining 1/2 teaspoon of salt, and the pepper, and cook, stirring, until soft, about 4 minutes.
Add the flour and cook for 2 minutes, stirring constantly.
Whisk in the milk and bring to a simmer over medium-high heat, stirring occasionally. Simmer for 2 minutes. Remove from the heat.
Add the cheese and peas and stir well.
Add the cooked noodles and drained tuna and stir well.
Pour the tuna mixture into the greased casserole dish.
Top with the crushed potato chips and bake until golden brown and bubbly, about 20 minutes.
Using the mitts or pot holders, remove the casserole dish from the oven and let rest for 5 minutes before serving.
Yield: 6 to 8 servings
Be extra careful removing the hot casserole from the ovenσitνs not just hot, itνs heavy, too!