For the cake layers, whisk 10 egg yolks in a clean and dry bowl at high speed of the mixer. Reduce the speed of the mixer, gradually add the powdered sugar and continue whisking. Whisk until thick and shiny mixture. Scrape the leftovers on the rim of the bowl once in a while with a plastic spatula.

Add the lemon juice and beat by increasing the speed of the mixer for 5 minutes. Again, reduce the speed of the mixer and slowly add the flour. Scrape the edges of the bowl again with a plastic spatula. On the other side, in a clean and dry glass bowl, whisk 7 egg whites with a pinch of salt with a mixer until it reaches a thick consistency. Feed the egg whites to the egg yolks with a wooden spoon. Divide this mixture into 5 equal parts. Cover the inside of a 20 x 10 cm wide baking tray with greaseproof paper and pour the first mixture.

Bake in a preheated 200 degree oven until the color turns slightly. Continue to cook the remaining 4 pieces of mixture in the same way (each time with a new greaseproof paper). Let the cakes cool at room temperature. For the filling, melt the chocolate in a double boiler and warm it. Whisk the butter with a mixer and rise. Add the melted chocolate, vanilla extract, egg yolks and powdered sugar into it and beat again with a mixer to mix well.

Carefully remove the cakes from wax paper and spread the chocolate mixture you have prepared between them. For the top, melt the dark chocolate and cover the cake and the sides. Leave it in the refrigerator for 1 hour, decorate with caramelized orange slices, and serve by slicing.