I've been looking a way to introduce a topic when I think of something without just blurting out a new subject.
Say you're having a conversation about Oreos and how there used to be gingerbread Oreos (a real conversation topic I just had) and you wanted to say "speaking of things that are made with gingerbread, have you ever heard of X / there's this other thing."
Maybe "speaking of X" is a little different (I'm not entirely sure) like someone having a conversation about Donald Trump and you want to say "speaking of Donald Trump, have you heard about his scandal?" But maybe they're functionally the same.
Either way, is there an expression for this?