Step 1

For the shrimp broth, in a large pot combine the shells, fennel, onion, carrots, garlic, bay leaf, salt, peppercorns and water. Bring the mixture to a boil. Lower the heat and simmer the mixture for 30 minutes, uncovered. Pour the broth through a mesh strainer or colander into a saucepan or large bowl and keep it warm.

Step 2

For the paella, heat a 14- to 16-inch (36- to 41-cm) paella pan or a large (12- to 14-inch [31- to 36-cm]) pan that has at least 3-inch (8-cm) sides over medium-high heat.

Step 3

Add 1 tablespoon (15 ml) of the oil, the chicken and chorizo and cook until the chorizo is browned and the exterior of the chicken is opaque, about 10 minutes total (do this in two batches if your pan is less than 14 inches [36 cm] in diameter). Sprinkle the meat with 1 teaspoon of salt, then remove it to a plate, using tongs.

Step 4

Add the remaining 3 tablespoons (45 ml) olive oil, the onion, bell pepper and garlic to the pan. Cook, stirring, until the vegetables are softened, about 5 minutes.

Step 5

Add the tomato paste, paprika, black pepper and cayenne to the pan, and stir to coat them with the oil. Stir in the rice, reserved chicken and chorizo, 1½ teaspoons (5 g) of salt and the shrimp broth.

Step 6

Bring the mixture to a lively simmer and cook it for 18 to 20 minutes, uncovered, until the liquid is almost absorbed and the rice grains rise to the surface of the pan.

Step 7

Arrange the shrimp over the top of the rice, lower the heat to medium low and cover the pan. Cook until the shrimp turn pink and are cooked through, 7 to 10 minutes, depending on the size of your shrimp.

Step 8

Sprinkle the cilantro over the paella, squeeze the lemon over it and serve.