Boil pasta according to package directions. In large saucepan, melt 1/2 c butter over medium heat. Whisk in flour and cook for 2-3 minutes. Add garlic salt and pepper to taste. Slowly pour in 4 cups milk, whisking until smooth. Heat to a low boil until thickened. Remove from heat.
Add hot pasta to a greased 9x13" baking dish. Sprinkle 6 cups shredded cheese over pasta. Pour the thickened cream sauce over the pasta and cheese. Let sit until the cheese has melted and stir together.
Melt 2 TB butter over medium heat. Add in bread crumbs, stirring constantly until golden brown, about 3-5 minutes. Pour over the mac and cheese.
Bake at 325 for 14-15 minutes. Serve warm.
