Place the potatoes in a pot and cover with cold water. Bring to the boil and simmer (uncovered) on medium heat for 15mins until tender.
Whilst the potatoes are cooking, in a frying pan, heat the oil and add the onion. Stir-fry on medium-low heat for 3-4mins until soft and golden.
Then add the garlic, turmeric, cumin, coriander, black pepper and stir-fry for a further 30secs-1min to lightly cook the spices and set aside.
Place the fish into a microwavable dish and gently rub the butter into it. Spoon over half of the milk and cover the dish with either a lid (leaving a small vent) or cling film (piercing a few holes), and poach in the microwave on high for 1½-2mins until the fish is flaky and cooked through.
Check half way to ensure the fish is not being overcooked. Once the potatoes are cooked, drain and place in a bowl.
Spoon in the remaining 2 tablespoons of milk (along with the buttery milk the fish was cooked in) and mash the potatoes until smooth.
Add the spiced onion to the mash and flake in the fish, ensuring there are no sneaky bones left.
Combine together for a creamy, luscious pie. If the end consistency is too heavy for baby, add some extra milk.
Serve to your little one warm.
For more beautiful Indian baby and toddler recipes, visit Zainab Jogot Ahmed's website here