Place the fish into a wide-bottomed pan in an even layer. Pour in the milk and season.
Cover lightly with baking paper and place over a low heat. Bring to a gentle simmer for 5–8 minutes or until cooked.
Remove fish from the milk and chop into pieces and place into food processor.
Whisk 150mL (100mL if fortifying) of poaching liquid and Shape It into a saucepan, bring to the boil over medium heat. Simmer gently for 2 minutes, stirring occasionally.
Pour mixture over fish (if fortifying, add AdVital) and puree until smooth. Scrape down sides as required and blend thoroughly. Season to taste with salt and pepper.
Pour into the prepared mould or container, cover with cling film or mould lid, and refrigerate until set.
Remove from mould, leave whole or cut into bite-size pieces, and heat before serving.