Preheat oven to 200°C/180°C fan-forced.
Trim beetroot stems and leaves reserve small beetroot leaves. Wash beetroot and Pat dry it.
Cover beetroot tightly with foil. Place in a baking dish and roast it for 45 minutes, until skin peels way.
Cool it, Peel and halve each beetroot.
Heat oil in a large frying pan over medium heat.
Add garlic and walnuts cook it until walnuts are toasted.
Add reserved beetroot leaves to pan cook until leaves are just wilted.
Add leaves and vinegar to beetroot, season with pepper. Toss to combine.
Top with feta and serve it.