Start with marinating the chicken. Season chicken pieces with paprika, salt (asin), and pepper (paminta). Make small cuts in the meat for better flavor absorption and refrigerate for 30 minutes.
Meanwhile, prepare the seafood. Clean the shrimp (hipon) by removing heads and shells but keeping tails intact (tanggalin ang ulo at balat, pero iwan ang buntot). Clean and debeard the mussels (linisin at tanggalin ang buhok ng tahong). For the rice (bigas), rinse once and steep saffron (asafrón) in ¼ cup warm water for 15 minutes.
Heat the paellera or wide pan over medium heat. Add olive oil and cook sliced chorizo de bilbao until oils release, about 3-4 minutes. Remove and set aside, keeping the flavored oil in the pan. In the same oil, brown the marinated chicken pieces (5-7 minutes per side) until golden brown, then remove.
Create the sofrito base by sautéing minced garlic (bawang) until golden (1 minute), then add chopped onions (sibuyas) and cook until translucent (3-4 minutes). Add tomato sauce and cook until slightly reduced (5 minutes), scraping the bottom to release flavors.
Add rice to the pan and stir to coat with sauce. Pour in the saffron water and remaining warm water (mainit na tubig). Bring to a boil. Once boiling, STOP STIRRING (huwag nang haluin). Return chicken and chorizo, arranging in a decorative pattern. Reduce heat to low, cover with foil, and cook for 15 minutes.
Remove foil and arrange shrimp and mussels in a circular pattern, pushing slightly into rice. Replace foil and cook for 10 minutes. For the socarrat (tutong), remove foil and increase heat to medium-high for 2-3 minutes until you hear a crackling sound. Remove from heat, keep covered, and let rest for 10 minutes before serving.