Place potato in a large saucepan cover with water, bring to the simmer over medium heat and cook until tender (25-30 minutes)
Drain well, return to pan, mash add milk and 30g butter and mix until smooth, season to taste and set aside
Preheat oven to 180C. Bring stock, wine and 100ml water to the simmer in a large saucepan, add fennel and simmer until tender (8-10 minutes)
Add white fish, ocean trout and prawns and cook stirring occasionally to poach (2 minutes), drain and reserve poached seafood and stock separately. You will need 600ml stock
Melt remaining butter in a saucepan over medium heat, add flour, stir until sandy-coloured (1-2 minutes), add reserved stock stirring a little at a time, stirring continuously, then stir occasionally until reduce to sauce consistency (18-10 minutes)
Add cream and reduce until thick (15-20 minutes). Add Kikkoman Soy Sauce, stir to combine, set aside to cool slightly
Stir through herbs, poached seafood and smoked fish and spoon into a 2.5 L capacity oven-proof dish (or individual single dishes), top with potato mash, scatter with cheddar and bake until golden and cooked through (30-35 minutes)
