Preheat the oven at 165ºC (conventional oven)/160ºC fan oven
Sift the flour with the baking powder, baking soda, salt and spices.
Add the butter to the sugar and combine. Then add the buttermilk/yoghurt and beat until smooth.
Add the flour mixture and quickly knead into a ball.
Tip the dough on to worksurface. Form a ball
Flatten the ball into a disc shape, cover and rest in the fridge for at least 30 minutes - or even over night if you want make it in advance. This allows the spice flavours to develop.
Roll the dough thinly (about 3-4mm) and press out the biscuits with a cutter. The windmill cutter is traditional but you can use what you have available.
Bake in the oven for about 11 minutes, depending on your oven. Take them out and leave the speculaas on the baking tray for a few minutes to firm up. Transfer them to cool on a rack.