Combine both chocolates and melt them over a double boiler. Whisk the yolks and 1/2 of the sugar in a mixer equipped with a whisk, set aside at room temperature. In a separate bowl, whisk the whipping cream to the soft peak stage and set aside, refrigerated. Combine the 3 egg whites with the remaining sugar and whip to a soft peak stage. Pour the melted chocolate into the yolk and sugar mixture and whip at high speed until the mixture begins to pale and increase in volume. Fold in the whipped egg whites and then the whipped cream until smooth and homogenous. Pour into individual 3-inch diameter plastic round bottom (about 1/2 cup capacity) molds and freeze.
Combine and melt the Gandujia and the hazelnut paste over a double boiler until smooth. Set aside at room temperature. Add the royaltine chips and the peanut oil and fold into the chocolate mixture until smooth. While the mixture is still warm, spread it on a sheetpan in a 1/2-inch layer, evening the surface with the aid of an offset spatula. Refrigerate until solid and then cut into 3-inch circles and refrigerate. These circles will serve as the base for the mousse cakes.
Combine both of the ingredients over a double boiler and melt until smooth. Allow to cool to a warm stage and fill a container of an electric spray gun with the mixture. The spray gun should be new or has never been used for any purpose other than food.
To assemble cakes: Remove the crunchy 3-inch discs from the refrigerator and place on plates. Remove mousse molds and unmold on top of the disc. These should be kept frozen until ready to spray with the chocolate mist. Remove mousse cakes from the freezer and spray the chocolate domes liberally to create a velour type finish, while still frozen. Refrigerate until set. Serve the mousse cakes with chocolate sauce and chocolate decorations of your choice.