Preheat a large pan to medium heat. Add some oil for frying along with the celery, onion, and jalapeno. Cook until softened.
Add in the butter, Old Bay seasoning, and flour. Stir and cook for two minutes.
Gradually whisk in the milk and cook until a creamy sauce is formed.
Whisk in the Dijon mustard and sour cream until combined.
Add in one at a time until well combined the tuna, cheese, peas, and cooked egg noodles.
Cook in a large cast iron pan or a greased 13x9 glass baking dish.
For the topping
Add all the topping ingredients to a plastic bag. Crush the crackers and roughly combine all ingredients.
Add to the top of the casserole.
Bake in a preheated 350-degree oven for 25-30 minutes or until the top is a golden brown.
Allow to rest for a few minutes prior to serving.
Serve immediately or store in an airtight container for up to one week.
Notes
Note that cream of mushroom soup can be used in this recipe. Omit the flour, and add one can to the cooked vegetables. Add ½ - ¾ cups of milk to make a creamy sauce.