The New Xbox One Experience (NXOE) is available to test for select dashboard preview members, bringing shades of Windows 10 with it.
A keen reddit user recently discovered that you can access Cortana on the NXOE using a hidden menu item. Cortana is currently slated to appear on the Xbox One in early 2016.
If you're still outside the preview, I've put together a video to show how she works on the new dashboard, although I thoroughly expect she'll work a little differently when she ships to testers properly.
Full story from the WindowsCentral blog...