Cook the noodles, al dente and grate the cheddar cheese.
In the meantime, drain the tuna, slice the mushrooms and mix them in a casserole dish with the dry mustard, mayonnaise and cream of celery soup (you can substitute this with cream of mushroom soup but I prefer cream of celery).
Once the noodles are cooked, drain them and mix them in with the tuna mixture and shredded cheddar.
Pour the breadcrumbs over the top.
Bake the dish uncovered at 350°F for about 45 minutes.
Enjoy with a salad or something else green (and good for you).