Preheat oven to 375 and grease a 13x9 pan.
Boil water for egg noodles.
Chop vegetables.
Cook noodles for 6 minutes or half the package directions time, drain and rinse with cold water.
Melt butter in a skillet and add onion, celery and garlic. Cook until tender crisp. Salt to taste.
In a large bowl, combine tuna, soup, milk, cheddar cheese, peas, cooked vegetables, noodles and salt.
Pour into prepared pan making an even layer.
Combine cornflakes, cheddar cheese and parsley in a bowl. Add melted butter and mix until everything is coated.
Top casserole with buttery cornflake topping and put into oven for 20 minutes, or until golden brown.
Serve immediately with a little fresh cheddar and parsley for garnish.