Use a 7''/18 cm diameter cake ring or individual pastry rings. Line rings with acetate or parchment (it will ease removal). The use of gelatin isn't required if this dessert is built using a shallow dish just like a Tiramisu, Martini glasses, ramekins or cups...
Sift flour and cocoa powder and set aside. Use a water-bath by setting a large mixing bowl over simmering water or use direct heat as shown. Place the whole eggs and sugar in the mixing bowl and beat the mixture to 100ºF/40ºC. Continue whisking using a stand mixer on high speed until it thickens. The batter should fall back into the bowl in a thick ribbon. Carefully fold in the sifted dry ingredients. Do not over mix or the batter will deflate. Spread the chocolate genoise evenly over a baking tray lined with a greased parchment paper.
Bake in a preheated 375ºF/190ºC oven for about 8 minutes. Let cool completely before using. Can be refrigerated up to 8 days or frozen weeks.
Bring to a boil and set aside. Use syrup at room temperature.
Soak gelatin separately in cold water to soften, and drain. Microwave the soften gelatin for just a couple of seconds prior adding to each chocolate mixture. Whip heavy cream to soft peaks. Divide into 3 equal portions and keep refrigerated. Cut chocolate genoise into desired shape but smaller than the size of the ring; the genoise should not be visible. Moisturize it with vanilla syrup. *Pate a bombe is a mixture similar to Italian meringue but using egg yolks instead of whites. Combine the sugar and water in a small saucepan, and put a lid on for a couple of minutes. After boiling, remove the lid and bring syrup to 250ºF/121ºC. Meanwhile, beat egg yolks using a stand mixer fitted with the whisk attachment, until light and frothy. Slowly pour the hot syrup in thin stream into the egg yolks. Let run on high speed until the pate a bombe has doubled in volume and the bowl cools down. Divide pate a bombe into three 3 oz/90g portions. Set aside. For the first layer: melt dark chocolate over water bath, remove from the heat and mix in the pate a bombe, add melted gelatin and whipped cream. Fill cakes immediately and freeze for 20 minutes or until firm to the touch. For the second layer; mix the warm milk chocolate with the pate a bombe, add melted gelatin and whipped cream. Fill cake and freeze until firm to the touch. Repeat using the white chocolate mousse. Freeze cakes completely for at least 4 hours prior removing rings, or for up to 3 months.
Remove cake rings and let thaw overnight in the refrigerator. Dust cake with cocoa powder before serving. Enjoy!