In a pot, boil the beet(s) in water until tender. To test, poke a knife through the middle to check if it goes through easily; if it does, it's done. When done, drain, and leave to cool.
Rinse buckwheat with water. In a pot, bring 375 ml of water to a boil, reduce the heat, add the buckwheat and the juice of half a lime. Put the lid on, and let simmer on low heat until the buckwheat has absorbed all the water (should take about 10 minutes). Remove lid and let buckwheat cool until lukewarm.
Peel the horseradish, wash it, and grate it on a fine kitchen grater or in a food processor using the grating wheel (the one with fine holes).
Peel the cooked beet(s) and cube it finely.
Wash the celery and cut it into small pieces.
Gently mix the buckwheat with the celery, the beet, and the horseradish.
Stir in 2 tablespoons of oil, 2 tablespoons of rice syrup, and the juice of half a lime.