Serve stew with a crusty baguette for a satisfying off-the-coast dinner.
Preheat oven to 350°. Cut top of garlic bulb off just to expose cloves, and drizzle with olive oil. Wrap garlic in aluminum foil; roast 1 hour and 10 minutes. Set aside to cool. Squeeze garlic cloves out of bulb; discard papery skin.
Melt butter in a large saucepan over high heat; add ginger and clove-spiked lemon to pan. Add fennel wedges, onion, and squash. Cook, stirring frequently, 10 minutes or until vegetables are caramelized. Stir in roasted garlic cloves, wine, tomatoes, bay leaf, salt, and red pepper. Bring to a simmer; reduce heat to medium, cover, and cook, stirring occasionally, 15 minutes. Increase heat to high. Add mussels to pan; cover and steam 6 minutes or until mussels open. (Discard any that do not.)
Remove ginger and lemon from pan. Stir in fennel fronds, parsley, and lemon juice. Serve stew with a crusty baguette.