Line two baking trays with baking paper. Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). For the dough mix 125 g butter, 150 g sugar, vanilla sugar and 1 pinch of salt with the whisks of the mixer until creamy.
Stir in 1 egg. Mix flour, baking powder and baking soda and stir in.
For the cookies, use a tablespoon to place 12-13 piles of dough on each tray with a little space between them, press slightly flat. Bake one after the other in a hot oven for about 10 minutes. Let them cool down.
For the lemon curd, separate 3 eggs. Chill the egg whites. Rinse organic lemon hot, dab dry and finely grate the zest. Squeeze all lemons. Take off 1 teaspoon of juice, fill up the rest with water to 350 ml liquid.
Bring lemon water and zest to the boil with 150 g sugar and 1 tablespoon butter. Mix starch with 5 tablespoons of cold water until smooth. Stir into the boiling lemon stock and simmer for about 1 minute. Remove from heat. First mix 2 tablespoons of hot lemon cream with 3 egg yolks.
Then stir the egg yolk mixture into the remaining lemon cream. Pour lemon curd into a bowl. Let it cool down for about 30 minutes, stirring frequently. Spread it still warm on the cookies. Let them cool down.
Just before serving, beat the egg whites until stiff, adding 180 g of sugar. Finally add 1 teaspoon of lemon juice. Continue beating until a firm, shiny mass is formed. Pour into a piping bag with a large perforated spout and squirt small tips onto the tartlets.
Brown with a kitchen gas burner.