Preheat oven to 400 degrees F.
In a large pot, cook egg noodles according to package directions (about 8 to 10 minutes). Add frozen peas to the boiling noodles in the last minute of cooking. Drain and set aside.
In the same pot, melt 1 tablespoon butter. Stir in diced onion and celery, cooking on medium heat for about 5 minutes, until onion is translucent. Add in minced garlic and cook for about 30 seconds.
Add canned cream of mushroom soup and 1 cup milk to the pot, stirring until combined. Break up drained tuna into the pot and continue cooking until the mixture is just starting to simmer.
Remove from heat and stir in drained pimentos, peas and egg noodles. Fold together until well combined.
Season with salt and pepper. Transfer to a 3-quart casserole dish or cast-iron skillet. If using, sprinkle on grated parmesan or shredded cheddar cheese.
Melt remaining 2 tablespoons butter and stir in breadcrumbs. Sprinkle topping evenly over the casserole.
Bake for 25 to 30 minutes until topping is crispy and casserole is bubbly.
Serve.