Peter Soons recommends trekking company Himalayan Leaders:
… The service was perfect, they even carried satellite phones, and foremost the cook knew his job. Group size was 4 pax and from their headquarters in Kathmandu, they called in every day to see how we were doing. …
They did this classic, one of our best hikes in Asia.
… an unforgettable 4 days to walk from Ganden to Samye in one of the most beautiful areas of Tibet. …
We trekked Ganden to Samye in 1998, independently and illegally. There were no guided tours at that time. 🙂
And we loved it.
besthike.com 
I can hardly believe this post … this indeed is one of the nicest hikes in the world, for the self-sufficient … I have never heard anyone mention it. Your write-up and rating was good. It’s too bad it’s being guided now, but guess that is the way things go.
I did it in 1987. Not sure how many “injies” had been over that route before; certainly less than 10. Ended up dancing the night away at a “dawa kokor” (full moon) festival in Samye.
Thanks for the memories.