I saw this recipe demonstrated on YouTube, and it made my mouth water. Chilcott is known as the One Pot Chef there and has a delightful Ausralian accent. I'm thinking about using reconstituted mixed dried mushrooms in this recipe.
Pour uncooked pasta into a large baking dish. Set aside.
In a large saucepan, gently heat olive oil, and add mushrooms. Turn them over, stirring, until they start to shrink down a bit and brown off. Add the celery soup and tuna and stir to combine thorooughly.
Add milk and water to mixture and stir until all ingredients are combined nicely. Bring to boiling, then pour on top of the pasta. It seems like a lot of water, but the pasta will soak it up.
Cover the baking dish with foil and place in preheated oven. Bake for 20 minutes. Remove the foil and bake 10 minutes longer.