Knead 125 g butter, icing sugar, flour, 1 egg and salt to a smooth dough. Wrap the dough in foil and chill for about 1 hour. Wash organic lemon hot and tear off the zest with a zest ripper. Put the zest in cold water and put it in the fridge. Halve remaining lemons, squeeze juice
Roll out the short pastry on a floured work surface until round (approx. 28 cm Ø). Line a greased tart mould (approx. 24 cm Ø) with the dough. Fold the protruding edges inwards and press down firmly. Prick the dough several times with a fork. Line the bottom of the dough with baking paper and fill in dried peas. Bake on the bottom shelf in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for approx. 10 minutes. Remove dry peas and baking paper and bake for another 10-15 minutes at the same temperature until golden brown. Remove the tart from the oven and let it cool down on a cake rack
Fill lemon juice with water to 500 ml liquid. Boil up lemon juice, 75 g butter and 250 g sugar. Mix starch and 4-5 tbsp. cold water until smooth and thicken the lemon juice. Mix egg yolks and 3 tbsp. hot cream, then stir into the remaining cream. Bring to the boil briefly and fill into the tart tin. Chill the tart for about 2 hours.
Whip cream until stiff, add vanillin sugar and 1 teaspoon sugar. Spread the cream loosely on the tart and decorate with lemon zests. Keep cool until serving and dust with icing sugar before serving
waiting time approx. 3 hours