Dirk is right. I have the overall snow with a soft reflection, and after that a surface shader, masked by tiny (0.01) fake stones with smallish density (0.1 or so), and a reflection shader as child. The fake stone shader acts as a very sharp mask, and is masked by a distance (10m or so) shader. The latter is quite important, or you'll have very sparkling areas very far, which is awful.
You'll have to play with values to test the best per scene.