Heat the lentils a saucepan with a teaspoon of olive oil until just warmed through. Add a splash of water if they start to stick. Remove from the heat and stir through the wholegrain mustard.
Put the mixed leaves into a serving bowl and top with the hot lentils, the quartered beetroot and the sliced goats’ cheese. Drizzle the remaining olive oil over the top and season with salt and freshly ground black pepper.