Discard any open mussels that do not close when tapped.
Cook mussels in white wine for 4 minutes and drain, reserving the liquid.
Remove most mussels from shells, keeping a few for garnish.
Sauté shallots, garlic, fennel, and curry powder in oil for 4 minutes.
Add stock, three-quarters of the mussels, and cream to the pan.
Warm through for 4 minutes, blend until smooth, and season with lemon, salt, and pepper.
Sauté carrot, fennel, leek, and mushrooms in butter until tender.
Drizzle baguette slices with oil and toast on a hot griddle for 3 minutes.
Place sautéed vegetables in bowls and pour the blended soup around them.
Garnish with oil, cress, and reserved mussels before serving with toast.