Tuna Mac and Cheese with Crunchy topping

Why I Love This Recipe
Whether you make this with tuna or without, it's still the best mac and cheese I've ever had.
Ingredients You'll Need
2 1/2 cups extra sharp cheddar cheese (it's best to buy block cheese and shred it yourself)
1 (6oz) can of Tuna(in spring water, drained)
3 Tbsp. butter
1/4 cup flour
1 tsp. salt
1/4 tsp. pepper
1/2 tsp. dry mustard
2 1/2 cups milk
Dash of hot sauce (amount depends on how much heat you like)
1 (8oz.) pkg. elbow macaroni (cooked al dente, drained well)
Crunchy topping:
3/4 cup dry bread crumbs
2 Tbsp. melted butter
2 Tbsp. chopped fresh parsley
3 Tbsp. shredded Parmesan
Directions
Melt butter in medium saucepan. Stir in flour, salt, dry mustard, and pepper until smooth. Remove from heat and gradually stir in milk until smooth. Stirring constantly, cook over medium heat until thickened (about 10 minutes). Remove from heat. Gradually stir in 2 1/2 cups cheese until melted. Add hot sauce and drained tuna. Mix well. Combine cheese mixture with cooked macaroni in greased 2 quart casserole. Sprinkle crunchy topping mixture over top of macaroni and cheese and bake in preheated 375 degree oven for 25 minutes.
Crunchy topping: Combine melted butter, bread crumbs, parsley, and parmesan and sprinkle over mac and cheese.