Put the haddock, chopped onion, water and bouquet garnet into a pan and bring it to the boil.
Cover the pan and reduce the heat to a simmer for 15 minutes or until the fish flakes easily.
Remove the fish with a slotted spoon and remove the skin and bones. Reserve the cooked fish flesh and toss the skin and bones back into the pan.
Simmer this uncovered for 30 minutes to create a lovely rich fishy stock.
Strain this fish stock and disscard the solids. Pour the stock back into your pan and add the chopped potatoes.
Simmer for approximately 20 minutes until the potatoes are tender and cooked through.
Remove the potatoes with a slotted spoon and mash them in a bowl with the butter.
Add the milk to the pan and bring to the boil.
Add the mashed potatoes to the pan and stir well.
Now add the flaked fish, season well and serve with a sprinkling of snipped up chives.