Finely dice the onions and sauté in olive oil. Add the dry rice and cook until translucent. Deglaze with wine, and wait until liquid is nearly absorbed, stirring constantly. Then add the first ladle of warm vegetable broth. Let the liquid evaporate before adding the next one. Finely chop the pre-cooked beetroot and add to the rice after 15 minutes. When the rice is al dente, reduce the heat. Stir the cold butter and then the grated parmesan into the risotto.
Sprinkle each serving with 1 tablespoon of chopped walnuts.
Tip: Also tastes good with horseradish. Serve the beetroot risotto with a tablespoon of horseradish sauce on top instead of walnuts.