Heat the oven to 200C/400F/gas mark 6. Place the beetroot in a small roasting pan with 125ml of water. Cover and cook for about 1 hour, until tender when pierced with a fork. Set aside to cool.
Peel and cut the beetroot into small dices. Transfer to a bowl and add half the coriander stem, mustard and red onion. Add half the lemon juice and 1½ tbsp oil. Mix well and season to taste. Cover and refrigerate.
Combine the salmon and the remaining coriander stem and red onions in a bowl. Add the parsley, and the remaining mustard, lemon juice and olive oil, season to taste. Mix well, cover and chill.
Cut the avocado in half, carefully remove the stone and use a large spoon to remove the skin. Dice into 0.5cm chunks, place in a small bowl and drizzle with lemon juice and a pinch of salt.
Curry leaf-olive oil:
Flash fry the curry leaves, allow to cool on kitchen paper and transfer to a blender along with olive oil and salt and blitz. Transfer into a squeeze bottle.
To finish: To serve, take four 8cm baking rings and place them on your serving plates. Put the diced avocado in the bottom of each ring, then top with an even layer of beetroot, then top with an even layer of salmon tartare. Pat gently to compress. Remove the rings, and garnish with micro cress and a drizzle of curry leaf-olive oil.