Put the prepared potatoes into a pan of boiling water and cook with the lid on until soft (around 15 minutes). Drain and leave to one side with the lid off

While the potatoes are cooking place the chopped onion and carrot into a large saucepan along with a little water and oil. Place over a low heat and sweat with the lid on until soft (around 10 minutes), adding more water if required to prevent browning and stirring frequently

Once soft, add the spinach or kale and cook for a few minutes

Remove the vegetables from the pan and place into an appropriately size deep sided oven proof dish

Next add the cornflour to the same saucepan along with approx. 5 tbsp milk. Mix into a thick paste then add the remaining milk. Place the mixture over a medium heat and whisk continually until thick and boiling

Remove from the heat and whisk through the mustard, nutritional yeast, lemon juice and parsley. Taste and season with salt and pepper

Finally add in the fish and bring back to the boil then add the cooked vegetables back into the mixture and stir to combine

Pour the mixture back into the oven proof dish

Mash the potatoes with a large glug of olive oil, salt and pepper

Dot the mash over the top of the fish mixture, spreading it out gently with a fork

Sprinkle with more nutritional yeast and bake at 200 degrees/180 degree fan for around 20 minutes until the fish is cooked and the top is golden

Serve with fresh green vegetables