Put the milk, egg, oil, and sugar in a bowl, and mix well until everything combines and the sugar melts.
Put a few drops of lemon juice over the ammonium (it will start bubbling).
Add it to the wet ingredients and mix it well.
Add the salt.
Start incorporating the flour, bit by bit, until you get an elastic dough, oily, that doesn’t stick.
Let the dough rest for 30 minutes.
Divide the dough into 3 equal parts.
Roll each dough thinly into a rectangular shape, to fit on the back of the tray you will bake it on.
Bake each sheet on baking paper, the back of the tray, for 15 minutes, at 150 degrees Celsius.
Let them cool down.
Start making the cream by mixing the flour with the sugar and the lemon zest.
Add the milk slowly and mix well, as you would make a roux.
When you finish adding the milk, put the pot on a low heat.
Whisk continuously for around 20 minutes, until the cream thickens and resembles a custard.
Turn the heat off and add the lemon juice and the vanilla essence.
Mix well and let to cool.
After 15-20 minutes, start whisking the butter, piece by piece.
Don’t over-whisk, as you risk splitting the cream.
Place a large piece of cling film over the baking tray you used to bake the sheets on.
Add the first layer of the cake, and cover it with a generous amount of cream.
Add the second layer, and repeat.
Add the third layer, and finish it with the rest of the cream.
Cover with coconut flakes.
Wrap the cake with the rest of the cling film and place a chopping board on top.
Add a heavy object on top, such as two books, and put the tray in the fridge.
Let it sit for 12 hours, better overnight.
Cut it and serve it at room temperature.