Blend until combined but still retaining some texture – it needs to be sticky enough to be able to easily stick together. However, be careful not to over-blend, as the mixture will become very greasy as the oils will be released from the nuts.
Transfer the mixture to a loaf tin lined with greaseproof baking paper (I used a one-pound loaf tin).
Smooth over the top .
Decorate with chopped pistachios, desiccated coconut and freeze-dried raspberries, if desired.
Place in the fridge for at least 30 minutes for it to firm up before cutting.
Remove from the loaf tin and cut into bars - you should be able to cut into 6 bars.
Keeps covered in the fridge for a good few days.
For a nut-free version, use sunflower seeds instead of walnuts, and use tahini instead of almond butter.