Preheat the oven to 400 degrees F.
Season the chicken with 1 teaspoon salt. Heat 1 tablespoon olive oil in a 10-inch skillet over medium-high heat. Sear the chicken on all sides until almost cooked through and beginning to brown, 5 minutes. Stir in the chorizo; cook until it releases its oil and begins to brown, another 5 minutes. Stir in the onions and garlic; cook just until the garlic is toasted and the onions are slightly softened, 2 minutes more. Stir in the chicken stock, clam juice and fire-roasted tomatoes. Add the peas, paprika, saffron and 1 tablespoon salt. Increase the heat to medium and slowly bring the liquid to a boil.
Meanwhile, lightly spray a baking sheet with canola oil. Spread the rice evenly onto the tray and lightly spray with more canola oil. Toast the rice in the oven until light golden brown in spots, 10 minutes.
At this point, the chicken mixture should be boiling. Ladle it evenly over the rice and return the baking sheet to the oven. Cover the paella by inverting another baking sheet and placing it on top. Bake until the liquid is completely absorbed and the rice is cooked through, about 20 minutes. Carefully remove the top baking sheet, and then remove the paella from the oven. Preheat the broiler.
Sprinkle the shrimp with 1/2 teaspoon salt. Combine the shrimp with the clams and mussels in a large bowl.
Arrange the shrimp, clams and mussels on the paella with the shell openings facing up. Lightly drizzle with 1 tablespoon olive oil. Broil--keeping a close eye--until the shrimp are cooked through, the clams and mussels have opened, and the rice is crispy, 2 to 3 minutes for a top broiler or 5 to 6 minutes for a bottom broiler. Sprinkle immediately with the olives and parsley.