Wash the rice and place in a saucepan. Cover with water and boil for 15 minutes. Remove from the heat.
Wash and finely chop the parsley and mint and add to the rice.
Dip the vine leaves briefly into boiling water and spread out on a tea towel to drain. Cut out the stems.
Drain the rice and place in a large bowl.
Peel and finely chop the onion.
Add the onions to the rice. Add half the lemon juice and 2 tbsp oil and mix well. Season with salt, pepper and allspice. Spoon about 1 tbsp onto each vine leaf.
Fold in the leaf edges and roll up from the stem end to the tip. Repeat until all the vine leaves are filled.
Place all the rolls close together in a pan and sprinkle with the remaining lemon juice and oil.
Pour in enough hot water so that all the rolls are covered. Place a small plate on the rolls and simmer over a low heat for 1 hour, then allow to cool in the pan. Drain before serving.
For the tzatziki cream, mix all the ingredients together. Serve as dip to the dolmades.