Make homemade Cream of Celery Soup. In a large saucepan over medium-high heat, melt butter. Add celery and onion and cook until soft, about 8 minutes.
Add garlic and cook another 2 minutes.
Add broth and bring to a boil.
Add tarragon, reduce heat to low and add the buttermilk and cream. Simmer until somewhat reduced, about 20 to 25 minutes. Season to taste with salt and pepper.
Use an immersion blender to blend until smooth or transfer mixture to a blender and blend until smooth. Measue out 2 cups to use for the casserole and you can freeze the rest for a later use.
Cook egg noddles according to package directions, but shave a minute or two off of the cooking time so that they are slightly undercooked. Drain well.
Preheat oven to 325 degrees and lightly grease a 9x13-inch baking dish.
Saute the celery and onion in the butter until soft.
In a large bowl, mix together mayonnaise, 2 cups Cream of Celery Soup, evaporated milk, 1 1/2 cups shredded cheddar cheese, the celery/onion mixture, the tuna along with the liquid in the can, peas, and pepper.
Stir in egg noodles. Transfer mixture to prepared baking dish. Sprinkle remaining cheese and potato chips on top. Bake for 30 minutes.