The secrets of Genoese Pesto in a marble mortar

Ingredients and doses (for 2 people)
25g of basil
35g of grated PDO Parmesan cheese
8g of pine nuts
1 pinch of rock salt
50ml of extra virgin olive oil
15g of grated PDO Pecorino cheese
1/2 clove of garlic

How it's done?
First you need to wash the basil, naturally Genoese PDO, in cold water, and then put it to dry on a cloth. In the meantime, in the mortar we begin to crush a clove of garlic (it must be sweet) for every 30 basil leaves (it is very important to respect the doses). We add a few grains of coarse salt.
When the garlic and salt have reached the consistency of a cream, add a handful of pine nuts. These will soften and blend the sauce.
At this point, add, but not all together, the basil leaves and start pounding them in the mortar with a gentle and prolonged rotating movement.
Let us remember that the essential oils of basil are preserved in the veins of the leaves and, to obtain the best taste, we must not pound too hard but rotate the pestle lightly, so as not to cut the leaves, but to tear them up.
It's time for cheeses. Parmigiano Reggiano and pecorino, both DOP and well seasoned. At the same time we add the extra virgin olive oil, poured dropwise.
Here we are, our Pesto Genovese is ready and can be used to season whatever we prefer.
If the Pesto is too "compact", adding the pasta cooking water will suffice to dilute the product.

Advices
The processing of Pesto must take place at room temperature and must be finished as quickly as possible to avoid oxidation problems (exposure to oxygen is one of the causes of oxidation).

Conservation
Keep the freshly prepared pesto in the refrigerator, in an airtight container, for 2-3 days, taking care to cover the sauce with a layer of oil. It is possible to freeze pesto in small jars and then defrost it in the refrigerator or at room temperature.
My partner who is a very good cook, once made a pesto with Shiso (Perilla frutescens) that we brought from Japan, and it was very delicious. He put the walnuts in place of the pine nuts. I'm sure you can make many other types of pesto. 

Is it different from that made in a blender?
Yes, it is different, although I can only say that it is strange. A mixer cannot do such a fine job of gently grinding the leaves without cutting the veins, and above all it is "time and effort". No matter how bad it is, a homemade pie tastes "more delicious" than a pie bought at a bakery, just as a mortar-made pesto tastes "more delicious" than one made with a mixer.