Kale Pesto...to blanch or not to blanch

Kale pesto appears to be the latest thing.  When I decided I wanted to make a batch with the kale I purchased at the market on Saturday, I took a look around the web to see how others were preparing it.  I was amazed to discover that many, many bloggers have posted recipes for kale pesto...  I thought there would be a lot of variations, but in reality there is very little variation from one recipe to another.  Kale pesto is by and large simply a kale variation of the classic pesto of basil, pine nuts, garlic, Pecorino/Parmesan and olive oil.  Most of the time walnuts are used instead of pine nuts...although I did see some versions that used pine nuts....or almonds...even pistachios.  Frequently lemon zest or juice or both are added to the finished pesto.  Occasionally I ran across a recipe that included hot pepper flakes and possibly the addition of another herb (like basil....or parsley), but in general, the recipes were about what I expected and what I (or any seasoned cook) would have made without the benefit of a recipe.    

While looking through all of these posts, I did discover what appears to be a great divide in the world of Kale pesto.   The split occurs between those who cook the kale and those who do not.  As I looked over the recipes I began to hone in on this difference...ultimately hoping that I could find a blogger who had addressed this issue head on and then explained their choice.  I never did come across such a post.  So while I was debating with myself: to blanch or not to blanch, it dawned on me that I could do both.....and report my findings here.

Two batches of Kale pesto--the quantities of all ingredients are identical.
 The batch on the left has been made with blanched kale...
the batch on the right with raw.

The good news is that both pestos were very good.  If I had eaten all of the pesto I made on the day I made them, the batch made with the raw kale would have won...no contest.  I do admit that when it first came out of the food processor, it was a bit chewier than I would like.  I had wondered if this might not be why most of the recipes I saw called for blanched kale.  But, after sitting for 10 or 15 minutes, it softened beautifully (just as whole raw kale leaves do in the presence of a vinaigrette).  Most importantly, the flavor of this batch was vibrant and strong—much more so than the batch made with the blanched kale.

If, on the other hand, I had waited to taste both batches until the next day, the batch made with the blanched kale would have won.  After sitting over night, the flavor of the cooked batch seemed to bloom, whereas the batch made with raw kale had lost some of its vibrancy (although, it was still very good).  Also, as one would expect the "cooked" batch held its rich, deep green color very well.

I had suspected when I made the two that the batch made with the blanched kale would be the better choice if I needed to make the pesto for longer storage (since the cooked kale will have a longer shelf life than the raw).  And this does seem to be the case.  If however you are planning on making and using your pesto right away, it is preferable to use raw kale.  Obviously the method you choose will depend on how and when you plan to use the pesto.     

I mentioned at the first that the nut used to make the pesto was one source of variation among the recipes I found.  I chose to use walnuts but when I was trying to decide which nut to use, I sampled some raw kale leaves not only with the walnuts, but also with some almonds and some pistachios.  Any of these would have been good.   In my informal sampling the bitterness of the walnuts provided depth to the taste of the kale, while the sweeter almonds and pistachios provided pleasant contrast.  I particularly liked the pistachios and will probably make my next batch with pistachios.  

Once you have made your kale pesto, just as with basil and arugula pesto, you will find all kinds of ways to use it.  On pasta, in soups, spread on a crostini or added to a sandwich....the list is long (as a quick google search will demonstrate).

So far, I have tried it tossed with green beans and cherry tomatoes and drizzled over poached new potatoes (to accompany pork).  I found that I especially liked it with the potatoes (no surprise there...kale is delicious with potatoes) and tomatoes.  For both of these uses, I let out the pesto (which I left quite "tight" when I made it) with a bit of the bean blanching and potato poaching liquid.  You could add more olive oil as well.

A spoonful or two of kale pesto "let out" with some green bean blanching water

For lunch today, I drizzled some (let out again with a bit of water and olive oil) over a platter of gnocchi tossed with roasted corn and poached zucchini.  This too was very good.   

Finally, for dinner this evening we had it on a pizza.  I made it in the style of an arugula pesto pizza I posted a couple of years ago, adding a layer of poached potatoes (8 oz. prepared as for Roasted Red Pepper and Potato Pizza) on top of the cheese.  As I expected, this was delicious too.    To make the pizza, scatter 3 oz. Fontina over the crust, followed by the potatoes, followed by 2 oz. of crumbled goat cheese. When the pizza comes out of the oven spread 50 grams of Kale pesto (thinned with a tablespoon of olive oil) over all.

So far, the pizza has been my favorite way to use the kale pesto.  But I've only scratched the surface.  I guess it's a good thing one bunch of kale makes such a nice generous quantity of pesto.

Kale Pesto

1 bunch of kale (I used Red Russian...but any kale should work), center ribs removed and rinsed in several changes of water (about 5 oz. trimmed weight)
2 oz. (1/2 c.) lightly toasted walnuts (or pistachios...or almonds...or pine nuts)
1 clove of garlic, peeled and smashed to a purée with a pinch of salt
2/3 c. extra virgin olive oil (more if you like)
1/2 c. (1 1/2 oz.) finely grated Parmesan and/or Pecorino (I like to use half and half)
1/2 t. kosher salt, or to taste
zest of a large lemon (optional)

Ingredients for 2 half batches. 
The blanched kale is on the left, the raw on the right.

If making the pesto with raw kale, chop the leaves medium fine.  (You will have about 4 cups packed chopped kale)  If making the pesto with cooked kale, bring a large pot of salted water to the boil.  Add the kale and cook until just tender.  Transfer the cooked kale to a bowl of ice water to stop the cooking process and set the bright green color.  Squeeze out as much of the water as you can and chop medium fine.

Place the kale, walnuts and garlic in the food processor and process until the ingredients are very finely and evenly chopped (stop the food processor a couple of times to scrape down the sides) to a coarse purée.

With the food processor running, add the oil in a thin stream. Scrape down the sides; add the cheese and pulse to combine. Add salt to taste and lemon zest if using.   Taste and correct the seasoning.  The recipe makes about 1 1/2 cups of tight pesto.  For most uses you will want to thin it slightly with water (plain or pasta/vegetable cooking water) or more olive oil.  

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