How to program a simple shader?

Hello!

I would like to know if there are any simple examples of how to program a shader in UE4. I’ve read about .usf files, but I still haven’t found a simple way to link these files to a material just so that I can create a really basic shader and go from there. I know there are VertexFactories and that the solution likely goes through there, but the few examples I find are too overwhelming for me to exactly understand the necessary workflow.

For me, the most basic example would be to just set the base colour to pure white (in the Material Editor this would just require linking a Constant value 1 into base colour). How would I do this with actual programming?

I hope I was clear. Thanks in advance!