1) Cook the macaroni according to package directions; drain. Start the cheese sauce by making a roux: Melt the butter in a heavy-bottomed saucepan over medium-low heat. When melted and foamy, add the flour and whisk together to form a paste.

2) Add 1 cup of milk; continue to whisk until mixture is blended and creamy. Start adding the cheese 1 cup at a time, stirring constantly. As the cheese melts, continue to add remaining milk and cheese in 1-cup increments. If the cheese sauce seems too thick for your liking, you can add in more milk as desired - just use small increments and keep stirring.

3) Add the white truffle oil once all the cheese and milk have been incorporated. Once the cheese sauce is fully melted