Ask HN: How do you get your startup okayed by a very large employer?

I work at a really large company, 100k+. I work on web apps on the side. I've read from several sources (Jason Cohen's blog, twist and startupcompanylawyer) that its not enough just to work on your own time with your own resources. You must also get someone with authority to sign off and acknowledge what you're doing. In such a large organization, getting a C*O isn't possible. Who would have the authority to officially clear your startup?