Rinse the courgettes and cut off the stalks. Slice off one end to array them upright. Cut off a slice from the other end to use later as a cap. Core the courgettes and chop the flesh finely. Warm ½ the olive oil in a deep frying pan and toss in the onions for 3-4minutes. Add the finely chopped flesh of the courgettes and carrots and stir fry them for another 2-3minutes. Finally add the minced meat and leave until it changes colour. Pour in the brandy and stir. Follow with the rice, herbs, salt and pepper. Add 1 teacup of water to get a mushy texture and combine everything well. Stuff the courgettes up to ¾ using a spoon. Cover with the slice you cut off earlier to use as cap. Place them upright in a narrow casserole and fill in the gaps with the potato slices. Sprinkle with the remaining olive oil and add enough water to cover the courgettes just above their middle. Tie the parsley and dill sprigs together and place them in the casserole. Season to taste. Put the lid on, bring to the boil and then simmer over medium heat for about 30min until the potatoes become soft and the rice bursts. Turn off the heat (if overcooked, the courgettes will become too soft and the rice sticky). Whisk the egg whites, add the yolks and then the lemon, a little at a time, while still whisking. Dilute the egg and lemon sauce with some food liquor and pour the sauce over the food. Holding the casserole by its handles, shake it gently right and left for the sauce to cover all its content.