Prepare the Saffron Infusion:
In a small bowl, soak the saffron threads in a tablespoon of warm water for about 5 minutes to release their flavor and color.
Cook the Vegetables:
Heat olive oil in a large skillet or paella pan over medium heat. Add the chopped onion and bell pepper. Cook for 4-5 minutes until softened and fragrant. Add the garlic and cook for another minute, stirring frequently.
Toast the Rice:
Add the Arborio rice to the skillet and stir to coat with the oil and vegetables. Cook for 2-3 minutes, allowing the rice to lightly toast.
Add the Broth and Tomatoes:
Stir in the smoked paprika and saffron infusion. Then, pour in the chicken or vegetable broth, white wine (if using), and diced tomatoes. Bring the mixture to a simmer. Season with salt and pepper to taste. Reduce the heat to low and let the rice cook for about 10 minutes, uncovered, until most of the liquid is absorbed.
Add the Seafood:
Place the shrimp, mussels, and fish fillets over the rice. Cover the skillet with a lid or foil and cook for 8-10 minutes, until the shrimp are cooked through, the mussels have opened, and the fish is flaky.
Serve:
Remove from heat and let the paella sit, covered, for 5 minutes. Garnish with chopped parsley and lemon wedges. Serve immediately and enjoy!