Start by making a spice paste: peel and roughly chop 1 of the red onions, the garlic clove, the ginger and turmeric, and pop in a small food processor with 2 tsp ground coriander. Roughly chop the coriander stalks (keep the leaves for later) and the chilli, flicking out the seeds and white pith for less heat. Add to the processor with 1 tbsp oil, a good pinch of salt and pepper and 1 tbsp Thai red curry paste. Blitz to make a smooth paste. No food processor? Simply finely chop everything and stir it together in a bowl. It will be chunkier than a paste, but it will still do the job.
Cut the ends from the butternut squash and halve it lengthways. Scoop out the seeds and discard them. Peel and finely chop the squash. If you have a food processor with a grater attachment, use that to coarsely grate the squash instead. Peel and thinly slice the remaining red onion.
Warm a large pan over a medium heat for 2 mins. Tip in 2 tsp fennel seeds. Toast for 2-3 mins till popping and spicy smelling. Tip into a pestle and mortar and crush lightly, or use a small bowl and a jam jar to roughly crush them. Set aside.
Place the pan back on the heat. Add your curry paste. Fry for 3-4 mins till aromatic smelling. Add the sliced onion. Crumble in the stock cube. Pour in the coconut milk and 400ml boiling water and give the pan a stir. Bring the liquid up to a bubble and simmer for 10 mins with a lid on.
After 10 mins, stir in the squash. Place the lid back on and cook for a further 5 mins.
Drop the fish pie mix into the fragrant broth. Place the lid back on and cook for 7 mins. The fish should be cooked through and the veg tender.
Finely grate in the lime zest and squeeze in the juice. Stir and add 1 tbsp tamari. Taste and add more till its to your liking. Ladle into warm bowls. Scatter over the toasted.