This is not possible with the existing API, though it wouldn't be difficult to add this functionality. What do you want to do with the Cookie afterward? Presumably just to_string() it? If so, then we can expose an API similar to that of Cookie::encoded().

Yes I use to_string() to send it to the client.

I also do it in reverse to validate the cookie:

let mut jar = CookieJar::new();
jar.add(Cookie::new("my_session", cookie2));
let cookie = jar.private(&key)
    .get("my_session")
    .map(|c| c.value().to_string());

I'd happily accept a PR that adds this functionality in the form of Cookie::encoded().

Closing due to inactivity. Still happy to accept a PR.