Bring water to a boil. Add the buckwheat and simmer on low heat for 20 minutes.
Cut the beef and onion into small pieces.
Heat roughly 30 ml oil in a large pan over medium-high heat. Add the beef and onion pieces and fry for 2-3 minutes until lightly browned, stirring frequently.
Add the vegetable stock and simmer on medium heat for 30-40 minutes until the beef is tender.
Remove from heat and stir in the whipped cream. Season with salt and pepper to taste.
Combine the cooked buckwheat with the beef ragout and stir well.