Preheat oven to 375°.
Melt butter in a large nonstick skillet over medium heat. Add the mushrooms; sauté 6 minutes or until soft. Add the peas, onions, bell pepper, and curry; sauté 5 minutes or until vegetables are tender.
Place flour in a small bowl; gradually add milk, stirring with a whisk. Add to mushroom mixture; bring to a boil. Reduce heat; simmer 2 minutes or until thick, stirring frequently. Remove from heat; stir in pasta, parsley, salt, and tuna. Spoon into a 2-quart casserole dish. Sprinkle with crushed crackers. Cover and bake 20 minutes.