Good question. And we don't have an answer, but they must surely have discovered some common interests as they have spent the last 52 weeks in each others company. That's a whole year, my friends.*
Mr Gaiman himself blogs very charmingly about his 52 week triumph over here.
Unfortunately we do not have a special pie to celebrate this wonderful achievement - but never fear, here are some cupcakes we prepared earlier. Congratulations Neil!
*We know that you know there are 52 weeks in a year. It was for dramatic effect. Forgive us.