General Cooking Questions

Hey there,
From What I know a velouté is a white roux with stock? 
I have Found a recipe for a sorrel velouté, (http://www.britishlarder.co.uk/oyster-beignets-with-a-sorrel-veloute/#axzz1yl8pyjBd)
Is this just a Modern Velouté using the Cream whipper to lighten the texture? 
 
would this velouté be possible to make using a classical base, aka a roux? (or any other vegtable based velouté for that matter.)