Heat the butter and oil in a large saucepan over a medium heat. Add the chopped beetroot, shallots, garlic, and thyme leaves. Cook gently for 3 minutes until the onion has softened, but hasn't colored.
Heat the stock to simmering point.
Add the rice to the pan and stir to coat all the grains in the buttery mixture. Cook, stirring, for another 1-2 minutes until the grains begin to look translucent.
Add the vermouth to the pan and allow it to bubble up and reduce slightly. Add a ladleful of the simmering stock, and stir until all of the liquid has been absorbed. Continue adding the stock, a ladleful at a time, as the liquid is absorbed, stirring between each addition. You have to stir constantly.
Cook the rice until the grains are tender but still have a little bite. It will take at least 20 minutes.
This risotto really does need quite a lot of salt but if you've used good home-made stock the dish should already be quite salty. Add the cream if you're using it (it makes the dish richer and also a paler color so it's up to you whether you want it at all), the pecorino and parsley. Taste and adjust the seasoning and serve immediately. Please credit Diana Henry www.lovebeetroot.co.uk