Dust the steaks with a good pinch of salt and pepper. Pierce the steaks with a fork all over - this helps tenderise them. Pop them in a dish or on a plate. Mix 1/2 tbsp Dijon mustard with 1 tsp of the fennel seeds and rub this all over the steaks, on both sides. Set aside.
Peel and coarsely grate the beetroot. Halve, peel and finely chop the red onion. Finely dice the celery. Peel and finely chop the garlic.
Set a large pan over high heat. Add 1 tsp olive oil. Add 1 tsp of the fennel seeds and the chopped veg and garlic with a good pinch of salt and pepper. Lower the heat to medium. Stir and fry to 5 mins till softened.
Add the buckwheat. Stir for 1 min to toast a little. Pour in 400ml boiling water. Bring to the boil. Lower heat. Simmer 15 mins, stirring often, till the water had been absorbed.
Swirl the remaining mustard through the buckwheat kasha. Finely chop the chives. Fold half of them through the. Taste. Season to your liking with salt and pepper. Set aside, with the lid on, to keep warm.
Warm a frying or griddle pan over high heat. Rub 1/2 tsp oil into each steak. Press into the hot pan. Fry for 2-4 mins each side, or for a few mins longer for well done steaks or if they are very thick steaks.
Spoon the kasha into bowls. Add a spoonful of yogurt to each bowl. Thinly slice the steaks. Perch the steak on top. Sprinkle with the remaining chives to serve.