Heat the extra virgin olive oil in a wide paella pan or a large, wide skillet over medium heat.
Add the diced onion and minced garlic, sautéing until the onion is soft and translucent, about 5 minutes.
Stir in the chopped tomatoes, sliced roasted red peppers, and smoked paprika. Cook for 5 minutes until the mixture breaks down into a thick paste known as sofrito.
Sprinkle the Bomba rice evenly across the pan and cook for 2 minutes, stirring gently to toast the grains.
Crush the saffron threads and add them to the warm seafood broth. Pour the infused broth into the pan. Do not stir the rice from this point forward.
Bring the liquid to a gentle boil, then reduce the heat to a simmer. Cook uncovered for 10 minutes.
Nestle the shrimp and mussels evenly into the rice. Continue to simmer for another 8 to 10 minutes until the seafood is cooked through, the mussel shells open, and the liquid is mostly absorbed. Discard any mussels that do not open.
Increase the heat to medium-high for 1 to 2 minutes to create the socarrat, the crispy crust at the bottom of the pan. Listen for a faint crackling sound and watch carefully to avoid burning.
Remove the pan from the heat, cover it loosely with foil or a clean kitchen towel, and let the paella rest for 5 minutes.
Garnish with freshly chopped parsley and serve immediately directly from the pan.