Melt the butter in a large saucepan.
Sauté the garlic and shallots for one minute without browning.
Add the mussels, half the basil, wine, and pepper to the pan.
Cover and cook over high heat for 4 minutes.
Remove mussels and strain the cooking liquid through a sieve into a saucepan.
Simmer the liquid for 10 minutes over low heat.
Add remaining basil and tomatoes and infuse for 8 minutes.
Remove mussels from their shells and discard any that did not open.
Wrap each mussel in pancetta and thread 10 onto each skewer.
Place the skewers on a baking sheet.
Cut baguettes into 8cm barrels, hollow out the centers, and bake.
Grill the skewers for 2 minutes on each side under medium heat.
Top with mozzarella and grill for 1 minute until melted.
Place the bread barrels in deep serving dishes.
Fill the bread with mussel juice and top with a skewer.