When I was a kid, I categorized foods by their colors. All the best foods, like dinosaur chicken nuggets, pasta and Cheerios, were beige, and, as most kids know, the worst foods, vegetables, were green. For an embarrassingly long time, I refused to eat pesto solely because it was green, and you can probably imagine my surprise at finding out that there weren’t any vegetables involved at all. Ever since that fateful day, pasta with pesto has been one of my go-to meals. So, if you want something that’s quick, easy, and delicious, here it is.
Traditionally speaking, pesto has only five (or six) ingredients: pine nuts; garlic; basil; olive oil; cheese (either Pecorino Romano, Parmigiano Reggiano or some combination of the two); and salt. The process is also straightforward: simply grind together all the ingredients and you’re done. But, with such a simple recipe, getting the most flavor out of each ingredient is key.
My biggest piece of advice: ditch the blender or food processor and make it by hand. It might sound like a lot of work, but if you’re adding your pesto to pasta, then you’re probably also standing around waiting for the water to boil and for the pasta to cook, so you might as well take that time to make a better pesto.
Once you get the hang of it, you’ll have your pesto done just before your pasta, which means that you can be eating a great, handmade pesto in under 15 minutes. In my opinion, cooking things by hand makes them taste much better. If you want the most flavor, as the Italians have always known, the mortar and pestle is king (or maybe there was just a blender shortage when they started making pesto, it’s hard to be sure).
To understand why the mortar and pestle method is superior, we have to talk about the science behind garlic and basil. This is going to involve some chemistry, but I promise it’s worth it.
Let’s start with garlic. Typically, when we chop ingredients, we are looking to control how much time they take to cook. Garlic, however, does not follow this paradigm. The flavor we associate with garlic comes from a compound named allicin, produced through the reaction between a compound called alliin and an enzyme named alliinase. This reaction is a defense against bacteria and fungi, which means that it only starts to occur when cells are damaged.
It’s this piece of information that explains the different forms of garlic in the kitchen: the finer you chop garlic, the more cell damage you cause, and the bolder the flavor. So, for maximum flavor, we want maximum damage.
For this, the high-speed blades of a blender are good, but they are sharp and thin. Designed to slice, they will only damage the thin band of cells the blade contacts. The grinding action of a pestle acts more like a hammer, crushing everything it hits, and releasing more flavor. As a bonus fact, the alliin reaction is why cooking garlic mellows its flavor: the heat denatures the enzyme, which is why roasted garlic has no spice. It’s also one of the reasons why you should never, under any circumstances, cook your pesto.
Not only will cooking pesto destroy the garlic flavor, but it will also knock out the basil flavor. Basil’s key flavor compounds come from a combination of enzymatic reactions and essential oils.
If you’ve ever used fresh basil, you know it smells amazing, but get it on top of a pizza, and it tastes like a wet leaf. The reason for this is that the essential oils in basil are highly volatile. They vaporize rapidly into the air with a very small rise in temperature, which, chemically speaking, refers to the kinetic energy of the molecules.
Unfortunately for us, if the flavor is in the air, it’s not in our pesto. The violent action that a blender or food processor uses to puree the ingredients does a great job of making sure that happens.
One final note on ingredients: consider adding a little bit of butter. While not seen in “traditional” pesto, butter was actually used in the first written pesto recipe. It also happens to be an excellent emulsifier and will help to boost the creaminess of the final product.
If you’re going to use butter, it’s best to dial back the oil to balance out the additional fat. You will also probably want your pesto a bit thicker, since the butter will melt in the heat of pasta, loosening your pesto more than you might expect.
With all that in mind, here’s how I make my pesto.
Pesto
Ingredients
Instructions
Add the pine nuts to the mortar and grind until there are no whole pine nuts left
Add the garlic (peeled and with the end sliced off) to the mortar and grind until smooth. Adding a small pinch of (kosher) salt here will draw some moisture out of the garlic and act as an abrasive, speeding up the grinding process. Table salt will not work as well, and if you use it be very careful about how much you add.
Pluck the basil leaves from their stems and add to the mortar. Grind until smooth. Here is the process I use (see below for pictures of the different stages):
i. Begin by striking in a vertical motion in the centre of the mortar.
ii. Once the leaves have begun to release some oils and are turning a darker green switch to striking slightly off centre, allowing the pestle to slide to the centre at the end of each stroke. While striking, slowly turn the mortar to keep everything from not sliding out. Adding another small pinch of salt at this point will assist the grinding process.
iii. When the leaves have begun to form a paste, use a spatula to incorporate everything, then grind with a rotary motion around the mortar until the paste is smooth.
Add butter to the mortar and incorporate with the pestle.
Add the cheese and incorporate with a spatula.
Incorporate olive oil until the desired consistency is reached
– At this stage the best thing to do is add slowly. My goal is to get the paste as saturated with oil as possible without ending up with oil at the bottom of my bowl once I’ve eaten it.
Add additional salt if desired
– If heavily season your pasta water, you are unlikely to need to add any here