I used the pre-bagged cauliflower and steamed it in the microwave. Let is cool for a couple of minutes and place in food processor or high speed blender. Add the toasted walnuts to the food processor, salt, pepper, lemon zest and juice and blend well. Add the olive oil through the feed tube in a steady stream. Add the chopped rosemary and puree until smooth. Taste and adjust seasoning. You can add more oil or water if the mixture is too dry. This dip can be served warm. You can refrigerate the dip for up to a day ahead of serving. Garnish with olive oil and walnuts.