First up chop up the swede and carrot, boil up for 15 minutes or until cooked, drain and blend with a hand blender until you have a mash (I add in a tbsp milk to make a better blend), season and set aside.
Now for the Pie...
Place the fish in a microwaveable bowl, put 2 sprigs of thyme on top, cover with a plate and poach in the microwave for 4 minutes. Or poach in a pan if you prefer. Set aside with lid left on.
Melt the margarine in a heavy bottomed saucepan. Soften the onions and garlic in the margarine until they are covered completely and slightly translucent.
Add in the milk and simmer for 5 minutes while stirring to mix everything together.
Now sieve in the cornflour (really important as, if you throw it in, it will be very claggy and difficult to break down - honestly, I've done this and had to get the hand blender involved!!) and mix slowly over a medium heat until the sauce begins to thicken up.
Sprinkle in the crumbled cheese and season well with salt and pepper and lower the heat. Keep stirring every minute or so until the cheese has really broken down and started to melt.
Meanwhile, cook the peas in a ban of boiling water for 3-5 minutes until just cooked.
Now scoop the fish out of the bowl with a fork or slotted spoon and put it straight into the pan of cheese and onion mixture (bone before doing this if you need to! Mine didn't need it, but make sure you know which fish you are using and how boney it is!), don't break it up before adding as it should flake as you stir. Finally stir in the peas and remove from the heat.
Remove the shells from the hard-boiled eggs and chop up into pieces. Scatter around the base of an oven-proof dish.
Pour over the cheese, onion, fish and peas mixture and cover with the mashed swede and carrot mixture.
Sprinkle a little extra cheese on top and bake in the oven for 20 minutes or until the top is crisped.
Serve warm with broccoli or any other vegetables of your choice. I love that this is a really colourful dish.