Heat the olive oil in a large nonstick skillet over medium heat. Add fennel, onion, and garlic; saute 5 minutes. Add tomato and next 6 ingredients (tomato through pepper); bring to a boil. Add mussels; cover and cook 3 minutes or until shells open.
Remove the skillet from heat, and discard any unopened shells. Let mussels cool. Reserve 10 shells with meat intact. Remove the meat from remaining shells, and add meat to tomato mixture; discard shells.
Combine water and cornstarch; add to tomato mixture. Bring to a boil over medium heat, and cook 2 minutes, stirring constantly. Spoon 1 cup pasta onto individual serving plates; top each with 1 cup sauce, and 5 mussels in shells.