Preheat oven to 350°F.

Melt butter in a large saucepan on low heat. Add flour and salt; mix well. Cook 2 minutes or until bubbly.

Gradually add milk, stirring until well blended. Cook on medium heat until mixture boils and thickens, stirring constantly.

Reduce heat to low; simmer 3–5 minutes or until thickened. Add 1 1/2 cups cheese and cook until melted, stirring constantly.

Add macaroni and mix lightly. Spoon into a 1 1/2-quart casserole and sprinkle with remaining 1/2 cup cheese.

Bake 20 minutes or until heated through.