Wash the offal thoroughly and cut it in pieces (not very small, about as big as an egg, maybe slightly bigger). 

Wash the intestines thoroughly, as well. This is the most demanding and tiresome part of the whole process. 

After washing them with plenty of running water, turn them inside out so that they are thoroughly cleaned on the inside, too. How? I have learned a method, that of the "knitting needle", but I know that there are others around.  Use a knitting needle to push the edge of an intestine towards its interior and carry on pushing untill all the length of the intestine is passed through to the other side. This way, the intestine is turned inside out and you can carry on with washing it. If the intestines come from a suckling lamb this process can be "compromised" a bit. 

If you don't start immediately the preparation of the kokoretsi, you should keep the clean intestines in a bowl with water and vinegar (or lemon). This way, they don't smell and they whiten.

Use another bowl to marinate the pieces of offal. 

In a food processor, blend the garlic cloves with the oil (1 tbsp, maybe a bit more). 

Salt the offal with 2-3 pinches of salt and pepper. 

Add a bit of oregano (be careful, too much will darken the meat)

Add the garlic pesto (about 2-3 tsp). 

Mix thoroughly so the spices go everywhere. 

Leave the offal to stand for a while to marinate. 

Next, start  skewering the offal, alternating hearts, spleens, sweetbreads, caul fat etc., pressing lightly and making sure that the pieces stay together but not too tight. 

When you are done skewering all the pieces, you have to cover the offal with the intestines. 

At first, start by tying one end of the intestine at the lower end of the offal. Take it upwards and after securing it on the top part, take it donwards again. And once more upwards and downwards a couple of times, turning the skewer lightly so that the "routes" don't coincide and all the areas of the kokoretsi are covered. In this way, you hold the pieces together and they don't move. 

Continue going up and down, this time turning the skewer around and making sure that the intestines cover all the surface of the kokoretsi, wrapping all the pieces that stick out. 

As you go on and the kokoretsi is wrapped you will notice pieces of meat that escape your attention and stick out of the cover you are making. With the appropriate moves and turning the skewer, make sure to wrap them too. 

When the length of the first intestine is done, tie another at one end of the kokoretsi and repeat the wrapping until the offal is fully covered. 

Some people, instead of doing that for each intestine, they tie them all together at one end of the kokoretsi and they continue wrapping it with the bunch of the intestines making sure that they are always spread and don't fall on top of one another. 

When you finish wrapping it, leave the skewer vertical (and covered) for a couple of hours (even overnight, if you have the time)  before you place it over the fire so that the meat lets its excess liquids drain.

Now, the fire plays an important role in the success of the kokoretsi. That is what determines the roasting time (for a kokoretsi that is as thick as that in the video, about 8cm, it took about 2,5 hours) but also how juicy or dry it will be.

We roast our kokoretsi over a "good" fire, high at first, so that it slowly cooks on the inside and towards the end, lower it so that it gets that crispy, crunchy exterior while staying juicy inside.