For the den miso, place all the ingredients into a saucepan and whisk over a medium heat until the sugar and miso have dissolved. Remove the pan from the heat and set aside to cool. Store in an airtight container in the fridge.
For the steak, mix the tamarind paste, den miso, garlic and thyme in a bowl until well combined. Add the steaks, make sure they are well coated in the marinade and set aside to marinate for at least three hours, preferably overnight.
Meanwhile, for the besan chips, heat the oil in a heavy-based saucepan. Add the spices, ginger, chilli and coriander and cook for a few minutes until aromatic.
Sift the besan into a bowl, then whisk in the water until smooth.
Pour the paste into the saucepan, add the salt and pepper and stir over a moderate heat with a wooden spoon or spatula for 10-12 minutes, or until the mixture thickens and comes away from the sides of the pan (the process is similar to making firm polenta, but the besan takes a little longer to thicken).
Grease a small oven tray and sprinkle with the nigella seeds and a little polenta. Pour over the besan mixture, cover with a piece of greaseproof and quickly flatten out the mixture. Chill in the fridge until the mixture has hardened.
Heat a griddle or a heavy-based frying pan over a high heat until hot but not smoking (if the pan is too hot, the outside of the meat will burn before it has cooked enough.)
Brush the steaks with the oil and season with salt and freshly ground black pepper. Cook for 2-4 minutes on each side, or until cooked to your liking.
Transfer the steaks from the pan to a rack, cover with foil and set aside to rest in a warm place for up to 10 minutes (this helps the meat to ‘relax’ and maximises taste and tenderness).
Preheat a deep-fat fryer to180C/350F. (CAUTION: hot oil can be dangerous. Do not leave unattended.)
Carefully turn the hardened besan out onto a chopping board and cut into chips. Dust the chips with polenta.
Deep-fry the chips for 2-3 minutes, or until golden-brown. Remove from the pan with a slotted spoon and set aside to drain on kitchen paper.
For the watercress salad, whisk the pomegranate molasses, vinegar and olive oil together in a bowl until well combined, then season with salt and freshly ground black pepper. Coat the watercress with the dressing.
To serve, place the steak onto serving plates with the chips and watercress alongside.