Whip the egg yolks with the sugar until light and fluffy, then add baking soda, sifted flour and starch and vanilla.
Separately, whip the egg whites until stiff peaks, then incorporate them into the other mixture, stirring gently with a spatula to keep them from disassembling.
Pour the mixture onto the baking sheet lined with parchment paper (trying not to exceed the mold too much), level the surface and cook for about 10 minutes at 180 ° C in a preheated convection oven.
Place the edges of the mold on the base and cut out the shape internally.
Soak the isinglass in cold water (for at least 10 minutes).
Meanwhile, cut the dark chocolate into small pieces and melt it (in the microwave or in a bain-marie).
Whip the cold cream from the fridge.
Bring the milk and sugar to a boil in a saucepan, then add the lightly squeezed isinglass and stir to dissolve.
Incorporate the milk into the chocolate, stirring to obtain a uniform mixture, then also add the cream in the now lukewarm mixture (if you have a thermometer for cakes, it must be at a temperature of about 35-36 ° C) and mix gently with a movement from the bottom to top.
Transfer the mixture into the heart mold, level the surface, then place the previously cut base on top.
Press lightly with your hands to make the base adhere to the mousse, then let it rest in the freezer for at least 4 hours.
Prepare the mirror glaze (prepare the syrup of water, sugar and glucose by bringing them to full boil, then pour it over the chopped white chocolate, add the soaked and squeezed isinglass and blend for a long time with the blender at low speed and with a slightly inclined container. ; finally add the dye).
After 4 hours you can take the cake back, remove the mold, turn the cake upside down and proceed with the icing.
The heart cake with mirror glaze is ready, decorate and let it dry for a couple of hours before serving.