Toast the walnuts over medium heat in a saucepan for about 5 minutes. Cool.
Put 1/2 cup olive oil, lemon juice, garlic, cardamom and salt in food processor or blender.
Trim ends off cilantro tips and chop coarsely. Place half of cilantro leaves in processor. Using on/off turns, process until smooth. If too chunky, add 2 tablespoons of water.