Preheat the oven to 200°C/400°F/Gas 6. Line a 33 x 23cm (13 x 9 inch) Swiss roll tin with non-stick baking parchment. Place the haddock and milk in a shallow pan, bring to the boil, cover and simmer for 5 minutes or until fish is tender. Strain and reserve the liquor. Flake the fish, discarding any bones.

Melt the butter in a saucepan, stir in the flour and cook for 30 seconds. Off the heat gradually stir in 250ml (8fl oz) of the reserved liquor. Bring to the boil, stirring continuously until thickened. Remove from the heat and stir in the haddock, egg yolks and season with salt and freshly ground black pepper.

Place the egg whites in the Kenwood Bowl. Using the Whisk, whip the egg whites until stiff. Stir one spoonful into the haddock mixture, then lightly fold in the remainder.

Spread the mixture evenly in the prepared tin and bake for 12-15 minutes, or until lightly browned and just firm to the touch.

Meanwhile prepare the filling. Using the Food Processing Attachment fitted with the knife blade, chop the watercress. Add the crème fraîche and garlic and herb cheese and mix, using the pulse action, until just blended.

Turn the roulade out onto a sheet of non-stick baking parchment. Remove the lining paper and spread over the filling, leaving a 1cm (½ inch) border. Roll up from a short side, using the paper to help. Serve cut into slices, garnished with watercress or dill sprigs.