Dry-fry the fennel seeds until they release their aroma, add olive oil to the pan and crisp the garlic and onion.
Throw in the tomato, stir, then add the red wine and bring to the boil. Add the mussels, cover and steam until they open (5 minutes) shaking regularly.

Strain the mussels into a colander, discarding any that didn't open. Return the liquor to the heat and reduce to a sauce consistency.
Add the mussels back to the pan, stir and warm through, then serve in the pot or decant to bowls.