In a medium saucepan, heat the chicken stock until boiling.
In a separate large saucepan or paella pan over medium-high heat, heat the oil and add the onion, the garlic, the peppers, the saffron and the chorizo. Cook for 6 minutes or until vegetables are soft and chorizo is browned.
Stir in the rice, tomatoes and tomato paste until well mixed and cook for 5 minutes. Add the boiling chicken stock little by little, stirring each addition constantly until the stock is almost absorbed.
Cover the paella pan with aluminum foil, and cook for 20 to 25 minutes, until rice is tender. Add the shrimp and the scallops and let cook covered for 5 to 7 minutes more.
Decorate with the chopped parsley and lemon wedges.