PREPARATION 40 min (+ 6h rest in the fridge):
To make the shells, pour the icing sugar and the very fine-grained almond flour into a bowl. Mix the two powders that will make the tpt, in French tant-pour-tant. Place only 45 g of the egg whites into the tpt (at a temperature of 20° - it is preferable to use the egg whites and yolks separated the day before and stored in the fridge, covered with film with cuts, to let the humidity out) and mix with a whisk, until you obtain a creamy consistency without lumps. Then in a saucepan pour first the water, then the granulated sugar and heat it over a high flame. Pour the remaining 42.5 g of egg whites into the bowl of a stand mixer and turn it on only when the syrup starts to boil. As soon as the syrup reaches a temperature of 118°, reduce the speed of the stand mixer and pour it slowly over the whipped egg white. Continue to whip until the mixture reaches 50°. The egg white should be stable and shiny. Now incorporate the egg white into the first mass, to do so take 1/3 and add it to the almond mixture. Mix from the bottom up and then incorporate the remaining egg white in 2 more times. Now proceed with the actual macaronage, so mix vigorously to give the mixture an elastic and shiny structure. Transfer the mixture into the piping bag with a 12 mm smooth nozzle. Make little piles about 2.5 cm wide, trying to make them all the same size and spacing them out. Bake them in a static oven at 150° for about 15-18 min.
Make the white chocolate ganache, then chop it finely and transfer it to a tall, fairly narrow container. Bring the liquid cream and the seeds of the vanilla pod to the boil in a saucepan and as soon as it starts to boil, pour 1/3 of it into the container with the chocolate. Start emulsifying with an immersion blender and add another half of the cream. Emulsify and add the remaining cream. Once you have obtained a smooth ganache, add the softened butter and emulsify once again with the blender. At this point, transfer to a low baking dish, cover with cling film and leave to crystallize in the refrigerator for 2 hours at 4°. As soon as the macaron shells are cooked, remove them from the oven and leave them to cool completely. After 2 hours, transfer the ganache to a piping bag with a 10 mm smooth nozzle and fill the shells. The filling should be abundant and weigh about 1/3 of the macaron. Close by overlapping the corresponding shell to the ganache and let all the macarons rest in the refrigerator for at least 6 hours covered with cling film.