Preheat the oven to 200 C
Chop up the cauliflower roughly and steam for 10 minutes until cooked through. Place in a blender with the mustard, ½ tsp of salt, a big pinch of salt and the coconut cream. Blend for a few minutes until smooth.
Cut the fish into chunks and finely chop the spring onions. In a large pie tin place your fish, throw over some salt and pepper, add the peas, coconut milk and spring onions. Smear the cauliflower mash over the top and bake in the oven for 20-25 minutes until the fish is cooked through and the cauliflower a little crispy on top.