In a large pot, bring the white wine to the boil. Poach the mussels in the white wine for about 2 minutes, or until the shells open. Remove from the wine and allow slight cooling.
Remove the mussels from the shells and keep to one side. Place the shells back into the wine and allow to boil for 5 minutes to enhance the flavour. Strain the white wine through an oil filter/muslin cloth and keep the liquid (for later use). Discard the mussel shells.
Melt the butter and sunflower oil in a pot until hot. Add the onions and garlic. Sauté well. Add the fennel and potatoes, caramelising this really well.
Then add the Pernod, cream, milk, stock and white wine poaching liquid. Simmer until the potatoes are soft.
Add the 100g mussel flesh and remove from the heat.
Blend, strain and check seasoning. Add a little water if necessary, Pernod and lemon juice on final tasting.
When serving, heat up with the remaining mussels and garnish with fresh fennel and deep-fried nori seaweed (optional).