William Leara of Dell has a new blog post, with a tutorial on writing a UEFI hello-world app using the UDK.
“Hello World” Quick-Start with UDK2015
The objective of this post is to explain how to get started with UEFI development by getting the UDK2015 development environment up and running, creating a Hello, World example program, and running it in the UEFI shell. Once you can get a simple application built and running in a UEFI Shell, you can begin extending it to greater and greater sophistication![…]
http://www.basicinputoutput.com/2017/06/hello-world-quick-start-with-udk2015.html