macaroni and cheese

4 cups macaroni, cooked just until very firm
1/4 cup butter
1/4 cup flour
2.5 cups half & half
2 heaping teaspoons dry mustard
1 pound grated cheese
1/2 to 1 teaspoon salt
1/2 teaspoon cayanne pepper
1 teaspoon black pepper

melt butter and flour in large pot. whisk together over medium-low heat and cook for 5 minutes, whisking constantly. pour in milk. add mustard and whisk until smooth. cook for 5 minutes or until very thick. reduce heat to low. add all but 1/2 cup cheese and stir until melted. add seasonings. pour in cooked macaroni and stir to combine. place in baking dish and top with remaining cheese. bake for 20-25 minutes at 350.