Finance Cover Letter

I will be graduating from undergrad in May 2017, and I am looking to go into financial services. Recently, I have heard that a GS executive extended an interview offer to a candidate because the cover letter was very interesting. The candidate wrote about the universe/space. My question is, where is the fine line between talking about past internships/qualifications vs something that shows personality? For example, I have a strong passion for cook; I host cooking parties every now and then and have also worked as a chef. How can I incorporate my cooking interest into my cover letter to show that I am both professionally driven for finance and have an approachable personality? Thank you