This dish has been created by Mark Murphy for the Theatre of Food at the Electric Picnic 2016.
Prepare beetroot, orange and seaweed up to ten days beforehand to allow it to start to ferment.
Mix the beetroot, orange slices, seaweed and dill together in a large bowl. Add in the sea salt. Using your hands gently mix in the salt for about 5 minutes. Place this into a clear kilner jar. To reduce the amount of air within the jar use a piece of cabbage leaf or some cling film, put it on top of the contents and give it a little push down. Close the jar and leave it for at least 10 days. You can open the jar every few days to let out the excess gas.
Once it has fermented, there will be a slight acidic tang to it. You can ferment it as long as you like but remember that it will become more acidic the longer it ferments. To prepare the salad for this dish remove as much of the contents as you need, mix in a handful of rocket and some toasted hazelnuts, and drizzle it with some lemon juice and rapeseed oil.
Make the salsa up to 3 days before.
Mix all the ingredients together in a bowl. Mix it well for about 5 minutes to allow the salt to come in contact with all of the other ingredients. Place this in a kilner jar as you did with the salad ingredients. Leave this to ferment for 3 days. You can keep it for about 10 days in the fridge but to keep the freshness I find around 3 days is perfect.
Heat the mackerel on a tray in the oven for about 2-3 minutes (really you only need to warm it to take the chill out of it). Place some of the salad in the centre of the plate and put the mackerel on top. Drizzle some of the salsa over the mackerel.