Wash and drain the vine leaves. Peel and finely chop the onion. Wash the chilli pepper, cut lengthwise, remove seeds and cut into fine rings. Coarsely chop the pine nuts.
Heat the oil in a pan, fry the onion and chilli in it. Add pine nuts and fry briefly. Add rice, 1/2 teaspoon salt and 400 ml water. Cover and let it swell at low heat for about 20 minutes.
Wash the mint and cut into strips. Wash 1 lemon and grate the peel. Cut the lemon into slices. Fold the mint and lemon peel into the rice. Place 1 tablespoon of rice in the middle of each vine leaf.
Fold over two opposite sides of the leaves and roll them up tightly from the base of the stem. Place the vine leaves in a pot and cover with lemon slices. Pour on 1/8 litre of water and let it simmer at low heat for about 30 minutes.
For the sauce, grate the rind from the remaining 1/2 lemon, squeeze the juice. Mix yoghurt, crème fraîche, lemon peel and juice. Season to taste with salt and sugar. Drain filled vine leaves and arrange on a plate with halved lemon slices.
Add yoghurt sauce.