Blitz the beetroot in a liquidiser with a ladleful of cooking liquid.
Add all the remaining ingredients down to the oil and blitz until smooth. You're aiming for the consistency of thick yoghurt. Season to taste.
To serve, ladle the borani into a bowl, scatter with feta, walnuts and dill, then drizzle with olive oil.

8 medium beetroot, washed and scrubbed, boiled until tender, peeled and diced - keep the cooking water!
1 clove garlic, crushed
2 tsp ground cumin
1 tbs red wine vinegar
a pinch of sugar (you may not need this)
200ml Greek or natural yoghurt
75ml olive oil
To serve
160g feta, crumbled
80g walnuts, toasted and roughly chopped
8 sprigs dill, leaves picked
Extra virgin olive oil, to drizzle