Speaking of pesto comes to mind immediately the Liguria: it's in this beautiful region that, with skilful care, is born this sauce that is said to be even aphrodisiac.
The pesto sauce is a cold, synonym and symbol of Genoa and Liguria, which for decades was one of the most famous sauces and disseminated worldwide.
The first traces of the pesto are even on the 8th century and since then, the recipe has always remained the same, at least in the homemade preparation. To make real pesto alla genovese you need a marble mortar and a pestle of wood e. .. patience.

Garlic 2 cloves
Basil 4 small bunches leaf
Oil extra-virgin olive oil - 1 glass
Parmigiano Reggiano 3 tablespoons
Pecorino 3 tablespoons
Pine nuts 1 tablespoon

1 pinch sea bulk salt

To prepare the pesto alla genovese it should be first clarify that the basil leaves are not washed, but clean with a soft cloth, and it must be Genovese basil or from Liguria sort, a narrow leaves (and not that southerrn italian sort with big leaf, which has often an aroma of mint).
So put the basil leaves in a marble mortar with a pinch of salt (which will serve to better crush the fibers and to maintain a nice green color), the garlic, and with a circular motion of the pestle crush it but do not use violence, crush the ingredients to the sides of the mortar to obtain a bright green liquid.
Add the pine nuts and continue to beat with a rotary motion until you amalgamate well with the juice of basil and you will obtain a homogeneous sauce.
Now you can add cheese that will make it even more creamy sauce, and the last olive extra virgin olive oil that will be poured drop by drop.

To get a very good pesto alla Genovese basil leaves have to be dry, and should not be minimally stropicciate, since the rupture of vesicles containing the essential oils placed on top of the leaves, cause the oxidation of color and aromas, making the pesto dark green and with the grassy aroma.
To prepare the pesto alla genovese, use an extra vergine olive oil fresh and mature, because it act as well as solvent for the aromatic substances, provides the perfect mix, enhancing the aroma of basil and the spicy garlic mitigating.

Working with pesto alla genovese must be done in the less time as possible to avoid problems of oxidation.
If you want to use the blender is certainly better to opt for plastic knives, as the metal in fact have the defect not to release full flavor from the leaves, making the pesto bitter. This method is very common, may provide a more emulsified sauce, similar to a cream, and the advice I can give is to use the mixer to lowest speed possible, so as to avoid heating due to friction.