Preheat the oven to 400 degrees F (200 degrees C). Boil a large pot of salted water for the
Penne Pasta (4 1/3 cups)
Cheddar Cheese (2 cups)
and chop the
. When pasta is al dente (cooked but firm), drain and rinse with cold water. Set aside.
Sauté the onion in
Salted Butter (1/4 cup)
until softened and fragrant. Add the
All-Purpose Flour (1/2 cup)
and stir vigorously.
Milk (4 cups)
and whisk over moderate heat until smooth, thickened, and starts to boil. Remove from the heat.
Tuna in Water (2 cans)
Sweet Corn Kernels (1 can)
, 3/4 of the cheese, and
Italian Flat-Leaf Parsley (1 handful)
. Mix until evenly combined. Season well with
Salt (to taste)
Freshly Ground Black Pepper (to taste)
Transfer into a large baking dish and top with remaining cheese.
Bake in the oven for 20 minutes or until golden and bubbling.
Sprinkle with parsley or chives and serve immediately.