Soak the yellow split peas overnight or for at least 6 hours in cold water. Drain and rinse.
In a large saucepan heat the chopped chorizo stirring it around to release its juices. Do this for about 2 minutes and then remove the chorizo from the pan with a slotted spoon and set aside.
Add the diced onions and diced carrots to the chorizo juices in the pan and sauté until soft, about 8 minutes or so.
Once the onions and carrots are soft add back the chopped chorizo as well as all of the pre-soaked yellow split peas, mix together, and then add the 1.5 litres of chicken stock.
Simmer for about 1 hour until all the vegetables are soft. Stirring the pot occasionally.
Switch off the heat and allow the soup to cool a little.
Puree the soup in batches and put back in a saucepan.