Cook the rice mixture in boiling salted water for about 20 minutes. In the meantime peel and wash the cucumbers, cut them into quarters lengthwise and remove the seeds. Cut the flesh into pieces. Wash lamb fillet, dab dry, also cut into pieces.
Carve the chilli lengthwise, remove seeds and chop. Peel and finely chop the onion. Fry onion in hot oil. Add meat and fry for about 3 minutes, turning. Season with salt and take aside. Stew cucumber in the frying fat while turning for about 5 minutes.
Deglaze with 1/4 litre water, add sesame and chilli, bring to the boil. Wash mint, pluck or chop small leaves. Mix yoghurt, cornstarch and mint until smooth and stir into the pan. Heat the fillet in it.
Season to taste with salt and lime juice. Serve garnished with lemon and lime wedges and chilli.