Heat the oven to 350 F. Grease a casserole pan and set it aside.
Cook 1 pound elbow macaroni in a large pot of salted water until al dente. Drain and set aside.
Melt 3 tablespoons unsalted butter in a large saucepan over medium heat. Stir in ¼ cup flour and mix constantly for 3 minutes
Add 3 cups milk and bring it to a simmer. Simmer for about 5 minutes, until thickened. Add 1 teaspoon salt, 1 teaspoon black pepper, and ¾ of the cheese. Add the cooked macaroni and mix well.
Transfer the mac and cheese to a casserole dish. Top with the remaining cheese.
Combine 2 cups butter crackers and 2 tablespoons unsalted, melted butter. Top the mac and cheese with the crackers.