Preheat the oven to 400 degrees Fahrenheit.
Take egg, lemon rind, salt, vanilla and mix them well until, using an electric mixer, until the mixture becomes creamy.
Now you need to knead butter and then add it to the egg mixture that you creating in step 1. Combine the new mixture in the electric mixer and wait for the paste to form. Here, you need to make sure that the mixer is set to medium speed. Turn on the high speed for just a moment or two, or else, you may end in creating too much foam on the top.
Wait for few minutes to allow the dough to relax. Place the dough on a plain surface and roll it thin. Before rolling, create a thin layer of flour on the surface, which will prevent the dough to stick to the surface. Place it in the oven and bake for around 10 minutes.
Meanwhile, you can soak gelatine for around 15 minutes, in warm water. Also, bring milk to the boiling point.
Place sugar, salt, half of vanilla, and egg yolks in a large bowl and beat them all together, until a creamy mixture forms.
Now add half of the boiled milk over the egg mixture that you just created. Blend the mixture well, before adding it to the remaining boiled milk. Bring the milk back to heat and boil for another few seconds. When the mixture reaches the boiling point, remove it from the heat.
Now take gelatine and press it to remove any excessive water from it, before adding to the boiled mixture. Add in chocolate, and wait until the mixture becomes creamy. Fold in half of the whipped cream and vanilla, before filling in the prebaked pie shell. Place it in the refrigerator for around 30 minutes.
Take the pie out of refrigerator and use the remaining whipped cream as topping. Dust the top with grated chocolate.