For the spinach filling, remove the stems from spinach, chop roughly and wash thoroughly. Blanch in boiling water for 60 seconds, drain and refresh under cold running water (this helps to retain the colour).
Blend the spinach in a food processor and place in a mixing bowl. Add the butter (softened), crushed kasoori methi and salt. Put the mixture into a piping bag and pipe 1 pence coin-sized discs onto greaseproof paper and freeze for 1 hour.
Boil or steam the potatoes until tender, leaving aside to cool (try doing this the previous day). Peel, then mash the potatoes, then add the cumin seeds, chilli flakes, crushed whole coriander and salt. Mix together and set aside.
Put the sago into a strainer and cover with cold water. Put a damp cloth over the strainer and leave for 10 minutes, then spread the sago evenly over greaseproof paper and set aside.
For the Aloo Tikki, place a spoonful of the potato mixture into flexible round plastic moulds (about 1 inch tall and 1.5 inches in diameter). Make a depression in the middle and place into this one of the spinach discs. Finish with more of the potato mixture and press down firmly.
Place the mould filled with the potato cake on the sago and press down firmly again (this is done only on one side of the cake, to coat it with a thin layer of sago).
Release the potato cake from the mould and repeat the process until you have 12 cakes. Leave in the fridge for at least 30 minutes before cooking.
Heat a non-stick frying pan with a small amount of oil and add 3 or 4 of the potato cakes at a time, with the sago side down. Cook over a medium-low flame until gently browned at the edges. Turn over with a thin spatula and cook on the other side for a few minutes on until gently browned.
Serve the Aloo Tikki warm with date and tamarind chutney, micro cress and a sprig of fresh coriander.