Cover the bottom of a large skillet or deep saucepan with some of sauce. Add mussels and clams.** Cook over medium-high heat until shellfish open (mussels will open first), about 8 minutes. Tilt the skillet to pour cooking juices into stew. Add more broth if needed and taste, adding more salt and paprika if needed,
*You could make seafood broth from scratch if you frequent a vendor who offers white fish frames--mine does not, so lately I've been buying seafood broth in a box.
**I prefer cooking the mussels and clams separately—easier to distribute when serving-- but If you have a large enough saucepan, you could pile the mussels and clams on top of the stew; adjust cooking times in earlier steps to allow for this change.