Hi [First Name],
Enjoyed our conversation at [event] — particularly your take on [specific topic they talked about].
You mentioned [thing they're working on / struggling with]. That reminded me of [useful thing: an article, an intro, a tool, a lesson from your own work] — [link or one-line offer].
If it'd be useful to continue the conversation, I'm happy to grab 20 minutes in the next couple of weeks. No agenda beyond [shared interest].
Either way — good luck with [their project].
Best, [Your Name]