I recently just bought the book "User Story Mapping" written by Mike Cohn. And I think it useful to help an agile team explore a more thorough picture of key features rather a close-door discussion between stakeholders and product owners.

A more challenging issue is that how to inspire members to engage in such an event since you don't hold it often. In my opinion, it's important to cultivate members' product view when they are dedicated to crafting shippable increments with capabilities. Maybe you could take some time to write associated topics. 👍