Grilled Cheese with Guacamole

"[Photographs: J. Kenji Lopez-Alt] Note: I like to add tomato to my basic guacamole recipe for this application. Grilled cheese and tomato is just classic. If you want to go one step further, add some crispy bacon to the sandwich. About the author: J. Kenji Lopez-Alt is the Chief Creative Officer of Serious Eats where he likes to explore the science of home cooking in his weekly column The Food Lab. You can follow him at @thefoodlab on Twitter, or at The Food Lab on Facebook. Every recipe we publish is tested, tasted, and Serious Eats-approved by our staff. Never miss a recipe again by following @SeriousRecipes on Twitter!..."