Chop the onion and put it in a pan with a tbsp of olive oil. When soft add the asparagus tips.Put the cube and the water in a pot and bring to the boil. Add the rice and toast it for a little while. Add the glass of wine, increasing the heat to let the alcohol evaporate. When all the alcohol is evaporated, add vegetable stock to cover the rice and stir. Keep adding the vegetable stock and stirring until the rise is cooked (20 minutes for white rice, 40/45 for brown rice). Risotto should be creamy, but the grains should maintain a good texture. Serve hot and sprinkle with chopped parsley and freshly grated parmesan cheese (optional).