Wysiwyg, I wouldn't par boil for pesto - it will just go slimy, but certainly it should work raw. It will need olive oil, some garlic, maybe some lemon zest, and Nigella Lawson's secret in her rocket (aruglua) pesto: an anchovy or two. just whiz it all together in the food processor. The anchovies can't be tasted in the finished product, but they add a depth and savouriness to the sauce.