For the meringues:
Sift the almond flour and the powdered sugar in a medium bowl. Add the first batch of egg whites (55 gr) without mixing them.
In a small saucepan, combine the water and sugar and bring to a boil until it reaches 118′C. Meanwhile, place the second batch of egg whites in the bowl of a mixer equipped with the whisk attachment. When the sugar is at 115′C start beating the whites on medium speed.
Pour the sugar at 118′C over the egg whites. Beat until the temperature of the mixture drops to 50′C. Fold the meringue into the almond-sugar-egg white mixture until it’s homogeneous. Place in a large pastry bag with a plain #11 tip.
Place parchment paper on two baking trays and use a pencil to draw 1 1/2 inches circles to cover the surface with 1/2 inch in between. You should have 36 circles on each parchment papers. Turn over the paper so the pencil marks won’t transfer to the meringues.
Pipe rounds of the meringue dough onto the prepared parchment paper. Let the meringues out at room temperature for at least 30 minutes. This is a very important step, the piped meringue rounds develop a thin ‘crust’ over their surface.
Preheat the oven to 350′F. Bake the meringues for exactly 12 minutes. Open the oven door quickly-twice during cooking. When the cookies are cooked slide the parchment paper onto a work surface and leave them to cool.

For the ganache:
Chop the white chocolate and melt in a bowl on a bain-marie. Bring the cream to a boil. Pour the cream on the melted white chocolate in three addition. Remove from the heat. While it cools, chop finely the white truffle and add to the mixture.
Scrap the mixture in a pyrex dish. Cover with plastic wrap and let it cool in the refrigerator.
Toast the hazelnuts in a 350′F oven for about 15 minutes. While they hot, roll them in a strainer to remove the skins (i used a clean kitchen towel). Transfer to a plastic bag and hit it with a rolling pin to make smaller chunks.

To assemble:
Place the white truffle ganache in a pastry bag equipped with a plain tip #11. Garnish half the meringues with the ganache, insert a few pieces of toasted hazelnut and cover with the other half to make a “sandwich”. Refrigerate in an hermetic box for 24 hours. Let them come to room temperature before enjoying them.