Lightly crush the cardamom pods so that the seeds can be emptied out.
Grind the seeds in a pestle and mortar for a couple of minutes.
Mix the butter, sugar, syrup and treacle in a large saucepan. Heat gently until the butter melts, stirring continuously.
Turn off the heat, add the spices and mix thoroughly.
Add the baking powder and stir again.
Add the water and stir once more.
Add the flour and stir thoroughly until it is completely mixed in.
Empty the mixture into a bowl. When cool cover with cling film (food wrap) and then leave the dough to rest in the fridge overnight or, if you can, even longer (a week is ideal).
Preheat the oven to 200°C (400°F, gas 6, fan 180°C).
Take a small portion of the dough for a test bake and return the rest to the fridge. The dough will be very firm and hard to roll initially. Knead it to soften it a bit, but it is easier to work when it is cold and fairly stiff.
Roll it out thinly on a lightly floured surface or onto greaseproof paper. Cut into shapes using a biscuit (cookie) cutter.
Lift the biscuits on to cold baking trays (cookie sheets), lightly greased if not using greaseproof paper. Bake for 5-8 minutes until golden brown. Keep an eye on them as they burn very easily, but they should be crisp.
If the test batch spreads out and the biscuits lose their shape, add some more flour and do another test bake.
If the test batch is good, remove enough dough for another batch and return the rest to the fridge. Bake in batches until all the dough is cooked.
Once baked, leave to cool for a minute or two and then transfer to a wire rack to cool completely.