Blanching basil leaves for pesto: If it matters, how to do it

To blanch or not to blanch? That is the question when it comes to making basil pesto.

Many cooks blanch the leaves for a few seconds so the pesto retains a vibrant green color.

But will a few seconds matter?

After a few days, the big bunch of basil I bought recently at a weekend farmers market was starting to wilt a bit. The leaves wouldn't last much longer.

And so my thoughts immediately turned to pesto. For one thing, I had all the other needed ingredients: garlic, cheese, olive oil and nuts. Plus, I already had a plan for the pesto: I would use it as a spread for tomato sandwiches.

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If there's one thing that's constant about basil and pesto, besides the flavor, it's the color. Once basil leaves are chopped, sliced or pulverized in a food processor, the leaves will darken a bit. That's where blanching comes in handy. Blanching the leaves just a few seconds and then shocking them in ice water helps retain that brilliant green color.

The only drawback is that you sacrifice a smidgen of basil flavor. If you decide to blanch, it's best to dial back or adjust the other pesto ingredients (the garlic, cheese and salt) so they don't overpower the flavor of the basil.

You can always pump up the flavor of the pesto by adding a few non-blanched basil leaves, which won't impact the color. Or you can just skip blanching. You don't need to do it to make perfectly good pesto. It's all a matter of preference.

If you've never made pesto, it's a sauce consisting of crushed or chopped basil leaves, nuts, garlic (usually), a mix of grated Parmesan and pecorino cheese (or either one), olive oil and seasonings.

Here's how to blanch the leaves and make pesto:.

Wipe 2 cups of tightly packed basil leaves with a clean, damp paper towel. Have ready a bowl of ice water.

Bring some water to a boil. Blanch the leaves in boiling water for five seconds. (Yes, seconds.) Use a strainer or slotted spoon to remove the leaves and immediately place them in the ice water bath for several seconds to cool and stop the cooking. Remove the leaves from the cold water and dry well on paper towels.

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In a food processor, add two peeled garlic cloves, 2-3 tablespoons toasted walnuts (or pine nuts or almonds) and ¼ cup grated Parmesan cheese. Pulse a few times to chop. Add the blanched basil leaves.  Slowly drizzle in 6 to 8 tablespoons of olive oil. Taste and adjust seasoning as needed. Add a few pinches of salt and, if desired, freshly ground black pepper. Pulse to blend the ingredients into a smooth paste. Add more olive oil if the mixture is too thick. Taste and adjust seasonings.

Store in the refrigerator. Keep covered with plastic wrap directly on the pesto or freeze. The pesto will keep for several days and maintain its green color in the refrigerator.

Contact Detroit Free Press food writer Susan Selasky and send food and restaurant news to: sselasky@freepress.com. Follow @SusanMariecooks on X (formerly Twitter.) Support local journalism and become a digital subscriber to the Free Press.