Following the package instructions, cook the pasta until tender (but not mushy). Drain well.
In a large cast-iron or other heavy skillet, melt the butter, then whisk in the flour until there aren't any lumps.
Slowly pour in half-and-half and whisk until smooth. Bring to a boil and cook until thickened, about two minutes, stirring constantly so the bottom doesn't scorch.
Reduce heat to low, and stir in cheese until melted.
Add the drained macaroni to the cheese sauce, stirring until everything is heated through. Add any toppings you'd like.
