Finely chop onion, garlic and celery. In large frying pan, heat olive oil and saute onion, garlic and celery until clear. Add 1 1/2 cans of broth and bring to a boil.
Bring a large pot of 8 cups of water to a boil. Add pasta and cook according to directions.
Defrost peas by soaking in warm water; strain.
Chop mushrooms and cube potatoes. Microwave cubed potatoes for 3 minutes. Add mushrooms, peas and potatoes to mixture. Add salt.
Mix cornstarch with remaining 1/2 can of broth, and add to mixture. Heat until bubbly. Cornstarch will thicken the mixture. Remove from heat. Stir in drained pasta and tuna or chicken and transfer to a casserole dish.
Bake for 20 minutes.
This is a lovely alternative tuna noodle casserole.
Can use 2 medium potatoes in place of 3 small.
Onion and garlic can be replaced with 3 shallots.
If avoiding fish, use canned chicken instead of tuna. Read labels on the tuna as some contain soy.
Corn Substitutions: Corn is a common ingredient in products. Starch, modified food starch, dextrin and maltodextrin can be from corn. Consult with your physician to find out which corn derivatives you need to avoid. Many corn-free options are available in the US. Find out more about corn substitutions.
Gluten: Gluten is a protein found in specific grains (wheat, spelt, kamut, barley, rye). Other grains are naturally gluten-free but may have cross-contact with gluten-containing grains. Look for certified gluten-free products if you need to avoid gluten. Find out more about wheat and gluten substitutions.