Sauté the onion and garlic cloves in a little heated olive oil in a saucepan over medium heat for about 5 minutes. Finely slice the chorizo and add to the onions and garlic in the pan, cook for another 5 minutes. Then add the chopped tomatoes and tomato paste to the chorizo and onion mixture. Cover and simmer for about 5 minutes. Then season the mixture to taste and mix in the drained chickpeas. Let the stew simmer gently for about 10 minutes, season again if necessary. Serve hot.