To recreate Garten’s mac and cheese, cook pasta in salt water and make a mixture of cream, nutmeg, Gruyère cheese, cheddar cheese, salt, and butter in a bowl. Combine the pasta with the mixture and refrigerate it for 24 hours, and the next day, let the mixture sit for an hour at room temperature before adding more cheese, breadcrumbs, and butter and baking it for 20 minutes.