Cook up one box of pasta according to directions.
Spray 9 x 13 pan with non-stick spray.
In a bowl combine the following:
3 cans tuna - mostly drained (I used white albacore chunk)
2 cans diced tomatoes - mostly drained
1 can water chestnuts - drained and diced
1 can cream of chicken soup.
1 cup frozen peas
1/2 cup dijon mustard
Pepper and garlic powder to taste.
Return the drained pasta to the pot. Dump in the contents of the bowl. Stir until mixed. Pour into 9 x 13 pan. Top with shredded cheeese (of course!). Bake until warm, melty and yummy. About 30 minutes.