Toast the buckwheat grains in a dry pan for 4-5 minutes, until golden. If your buckwheat is labelled 'kasha' then skip this step (it's already toasted).
Add the buckwheat to a saucepan with the water. Bring to the boil and then reduce heat, cover and simmer for 15 mins until the water is absorbed.
Remove the buckwheat from the pan and put onto a baking tray or large plate in single layer and leave to cool until the buckwheat is approximately room temperature. Cover and store in the fridge (unless you're in a rush - this also tastes great as a warm salad!)
While the buckwheat is cooling, finely chop the preserved lemon, herbs and sping onions.
Mix lemon, herbs and spring onions into the cooled buckwheat together with the sumac and drained chickpeas.
Whisk the lemon juice with the olive oil and stir through the buckwheat tabbouleh. Add freshly ground salt or seagreens and pepper to taste.