Toss the green onion in some olive oil and salt
Flick on the barbeque or turn your oven on to broil
Broil or bbq until charred (slightly blackened)
Take off/out and let cool a bit, then chop roughly
Put everything else in a food processor or blender and buzz, then toss in the onions and buzz again. That's it! (you could also probably just chop the onions a bit more thoroughly and stir up the cheese, but it's true that the blender/food processor does make the whipping thing happen nicely)