Sheets: Put the yogurt in a small bowl and mix it with the ammonium bicarbonate then let it swell.
In a bowl, mix the butter with the sugar and salt powder. Add the egg and continue mixing. At the end, add the yogurt, mix, then add flour and knead a homogeneous and elastic dough, good to spread.
Divide into 4 equal parts, spread sheets and bake on the back of the tray for 10-12 minutes or until lightly browned on the edges.
Cream: In a saucepan mix the flour with the sugar, vanilla sugar and pour the milk little by little and mix. Put it on the fire and let it boil slowly until it thickens like a pudding. Remove from the heat, add the vanilla essence and butter. Mix well and then allow to cool slightly.
Place a leaf in a tray, grease it with a thin layer of raspberry jam and then add some of the sour cream. Continue in the same way until the sheets are finished. Lightly press over the cake to make a good grip between them (sheets) and leave until the next day, covered with cling film, to soften the sheets.
Glaze: In a saucepan, place the broken chocolate in melted pieces in the 5 lg of milk. Leave it until it is homogenous (if necessary, add a little more milk) then draw stripes over the cake.
Portion and serve.