Preheat the oven to 200C/400F/gas mark 6.
Add the oil to a roasting tray and heat it in the oven for 5 minutes. Then add the beetroot, plums and vinegar to the roasting tray. Season with salt and roast for 30 minutes.
Leaving a little of the stalk in place, slice the radicchio into thin wedges. Add it to the beetroot tray with the chilli, maple syrup or honey and a bit more salt, and give it all a good stir. Roast for a further 10 minutes.
Add the garlic and stir it through the contents of the tray, then remove the tray from the oven.
Sprinkle over the sesame seeds and herbs (if using) and serve.
You can use any bitter crunchy vegetable instead of radicchio. Chicory would work well, as would sliced cultivated dandelion. Any toasted seed or nut can be substituted for sesame. I have also tried this with blackberries and blackcurrants instead of plums and it worked wonders – beetroot loves any dark, rich fruit that has a little acidity. I sometimes like to serve this with watercress or rocket.