Brown the chicken and pork in the olive oil. Remove and reserve.
Saute the garlic, onions, and peppers in the reserved oil.
Add the rice, saffron and salt. Stir until the rice is coated with oil.
Add the stock and bring the mixture to a boil. Cover the pan and place it in a 400' (205'C) oven; cook the rice mixture for 8 minutes.
Place the clams and mussels on top of the rice. Check the rice periodically and add more stock or water if necessary. Replace the cover and return the pan to the oven for 5 minutes.
Add the shrimp, chorizo, Tomato Concasse, carrots, and peas. Return the pan to the oven and cook the paella until the shrimp is cooked through and all ingredients are very hot.
Garnish the paella with the olives and scallions. Drizzle with the juice of 2 lemons. Cover the paella pan and allow the paella to rest for 10 minutes. Wedge the remaining lemons and serve with the paella.