Heat your oven to 200°C/Fan 180°C/Gas 6. Set a roasting tin on the top shelf to heat up. Fill and boil your kettle. Scrub the sweet potatoes. Chop into 3cm-thick cubes. Tumble into the hot roasting tin. Gloss with 1 tbsp olive oil and sprinkle with salt and pepper. Roast for 30 mins, or till tender and golden round the edges.

Put a small pan on a medium heat and warm it for 1 min, then add the buckwheat. Toast for 2-3 mins, stirring, till it starts to smell nutty. Carefully pour in 150ml boiling water (it might splutter, so go a little at a time) and add a pinch of salt. Pop on a lid, bring back to the boil, then reduce the heat and simmer for 15 mins till the water is absorbed. Take off the heat and let the buckwheat sit in the pan, lid on, to keep warm.

Meanwhile, peel the red onion and thinly slice it. Slide the onion into a bowl. Squeeze in the juice from half the lemon. Add a little salt and pepper. Scrunch together, then set aside for 10 mins.

Spoon 1 tbsp tahini into a bowl. Peel and grate in the garlic. Squeeze in the remaining lemon juice and add 2 tbsp hot water and 1 tbsp olive oil. Stir to make a thick dressing.

Trim the woody cores out of the spring greens and thinly shred the leaves. Tip them into a salad bowl. Add the cooked buckwheat, roast sweet potatoes and the mint leaves. Pour in the tahini dressing. Toss to mix, then divide between 2 warm plates. Top with the red onions, pour over any lemony juices and serve.