Looks like he uses an Alpine Fractal as terrain (terrain tab -> create terrain -> alpine fractal).
The snow coverage is subject of experimentation of course.
I'd add a surface layer and increase it's default colour from 0.5 to something around 0.85.
Set slope restriction to a max of 75 degrees with 10 degree fuzzy zone and see how it looks.
Make crop renders and check whether you like how the snow covers the mountain shapes.
Adjust slope restrictions to your taste, as 75 degrees probably gives too much coverage, but only acts as a starting position.
Ultimately you may also try playing with the more advanced surface layer settings like Intersect Underlying.
I don't know whether you were at the webinar yesterday, but I discussed it briefly there.
Cheers,
Martin
