Is there a way to use UDK and Flash in the same project?

I.e: build a world in UDK and use Flash on top of it.

Any info would be a great help. Same as tuts or books on the subject.

Questions welcome.

Of course. The UDK has support for Scaleform which IS flash content that can be used for UIs. The new version supports AS3 as well. Scaleform is not flash player, but Scaleform can use SWF files... Not everything is supported but it is useful for making UIs.

Autodesk Scaleform is a Flash®-based user interface (UI) solution for PCs, game consoles, and consumer devices.

Autodesk Scaleform combines the power and performance of modern 3D graphics technology with the proven productivity and workflow of Adobe® Flash® and Creative Suite®, resulting in the faster creation of higher quality content. Its powerful features have made Autodesk Scaleform the trusted solution on over 800 projects, from big budget AAA titles to smaller budget casual games and consumer electronics.
[/quote]
source: http://gameware.autodesk.com/scaleform