Put the tamarind paste, soy and hot water into the smallest saucepan you have, and stir over a low heat to dissolve the tamarind. When it’s as smooth as you think you can get it – the tamarind paste I use says it’s without stones, but I do find the odd one, and I don’t bother to get rid of them – remove to a bowl or jug, whisk in the oil and honey, and leave to cool. Do not use until it is cold.
Put the bavette steak into a resealable freezer bag, pour in the cold marinade and squelch it about so that the thin steak is covered on both sides, then seal, lay on a plate and put in the fridge overnight or for 1 day.
Bring it back to room temperature, prepare a large piece of kitchen foil, then heat a ridged griddle till very, very hot. Lift the steak out of its marinade, letting any excess (and there will be a lot) drip back into the bag and then slap the meat on the griddle and cook for 2 minutes a side.
Immediately (I use tongs for all this) transfer the steak to the piece of foil and make a tightly sealed but baggy parcel, and let the meat rest, on a chopping board, or any surface that is not too cold, for 5 minutes. Then unwrap the foil, transfer the steak to a board, and carve in thin slices against the grain.