Step 1: Heat olive oil in a large paella pan or wide, shallow skillet over medium-high heat. Season chicken thighs with salt and pepper and sear until golden brown on all sides, about 5-7 minutes. Remove chicken from the pan and set aside.
Step 2: Add chopped onion and bell peppers to the pan. Sauté until softened, about 5-7 minutes. Stir in minced garlic, crushed tomatoes, and smoked paprika. Cook for another 2-3 minutes, stirring occasionally.
Step 3: Add the Bomba rice to the pan, stirring to coat the grains with the tomato mixture. Cook for 1-2 minutes.
Step 4: Pour in the warm chicken broth and the steeped saffron water. Stir gently to combine, distributing the rice evenly across the pan. Bring to a simmer.
Step 5: Return the seared chicken thighs to the pan, nestling them into the rice. Reduce heat to medium-low, cover loosely with foil (if your pan doesn't have a lid), and cook for 15 minutes without stirring. This is crucial for developing the 'socarrat'.
Step 6: After 15 minutes, uncover and add the shrimp and mussels to the pan, arranging them on top of the rice. Sprinkle with green peas. Continue to cook, uncovered, for another 10-15 minutes, or until the shrimp are pink and cooked through, mussels have opened, and most of the liquid has been absorbed by the rice. Discard any unopened mussels.
Step 7: In the last 2-3 minutes of cooking, increase the heat slightly to encourage the formation of the socarrat (crispy bottom layer). Listen for a gentle sizzling or crackling sound. Be careful not to burn it.
Step 8: Remove the paella from the heat, cover lightly with foil or a clean kitchen towel, and let it rest for 5-10 minutes. This allows the flavors to meld and the rice to finish cooking.
Step 9: Garnish with fresh chopped parsley and serve immediately directly from the pan with lemon wedges on the side.