Cool the whites in the refrigerator. Grind nuts in a blender into crumbs; fry in a dry frying pan over low heat until light brown. Remove from fire, let cool.
Pour the chilled proteins into a large bowl; beat with a mixer at low speed for 5 minutes. Then turn on medium speed and beat for another 5 minutes. Switch the mixer to the highest speed and beat for 12-15 minutes, until a thick, dense foam is obtained. Continuing to beat, add powdered sugar and flour to the proteins. Turn off the mixer after a minute. * Prick up some of the egg whites with a fork. If the squirrels reach for the fork and do not fall off, they are ready.
Preheat the oven to 150ºС. Cover the baking sheet with a sheet of parchment and lightly moisten with water, making sure that the water does not collect in drops. Put the whipped egg whites in a culinary bag and, squeezing them onto parchment in a circle, form a cake with a diameter of 20-22 cm. Place in the oven, immediately reduce the temperature to 140ºС. Bake for 1 hour. Turn off the oven and leave the cake inside until it cools down. Bake 3 more cakes in the same way. * You can put 2 protein cakes on a baking sheet at once.
While the meringue is baking, prepare the cream. Grind the yolks with sugar and vanilla sugar until white, pour in 100 ml of water, mix. Put on a pot of boiling water and boil, whisking constantly, 4 minutes, without bringing to a boil; remove from fire.
Beat butter until foamy. Add condensed milk, whipped butter, nuts, cocoa and cognac to the cream. Mix. Allow to cool to room temperature. Then beat again with a mixer.
Lubricate the cakes with the resulting cream, put one on top of the other. Put the cake in the refrigerator for 1 hour.