Place in a medium pot and cover with cold water, season with salt.
Cook over medium heat until soft, strain into a colander.
Pass through a potato ricer or a fine mesh drum sieve.
Weigh 450g of cooked potato and set aside.
FISH
In a small frypan, heat some canola oil.
Saute the fish pieces in two batches. Cook until the fish just starts to fall apart.
Set aside.
DOUGH
In a medium saucepan, heat the milk over a medium heat until just simmering.
Add flour and stir quickly until a dough forms, continue to cook over a low heat until it starts to leave a light film on the bottom of the pan and pulls away evenly from the sides.
Using a wooden spoon, mix in the weighed cooked potato.
Mix in the eggs and mix thoroughly.
Add the cooked fish.
TO COOK
Preheat oven to 180 degrees.
Heat the canola oil in a small deep fryer to 180 degrees.
Spoon 1tbsp of mixture into the hot oil and cook until lightly golden. Continue to turn the doughnut to cook it evenly.
Place doughnuts on a tray with a drying rack.
Once you have cooked the batch, place the doughnuts in the over for 3-4 minutes to finish cooking and prevent doughy centre.