Put the gelatin sheet in some cold water, or prepare by the instructions on the package. Cut the rhubarb and strawberries into small pieces, put them in a pan with sugar and cook for around 10 minutes, or until they are soft and a bit reduced. Blend them with an immersion blender and then mix in the gelatin so it melts in. Take the bottom part (the full part) of your silicone mould and place a cling wrap over it, now put the gelee on top and cover with the cling film, you should have a round disk shape that will fit into the mould later. Put it in the freezer for a few hours, until frozen.

Preheat the oven to 190°C and line a baking pan (34 x 38 cm, or something similar that fits two 18-19 cm diameter circles) with parchment paper. Beat the egg whites with honey until stiff peaks, about 4 min. Stir together the flour, pistachios and almonds. Add the mixture to whipped egg whites and stir it in gently with a spatula. Spread the batter on the parchment paper in two circles, each 18-19 cm in diameter. They really don't have to be perfect in shape and they can touch because you will cut them in 17 and 18 cm diameter circles after. Bake them for 8-10 minutes. Let them cool and cut out one 17 and one 18 cm circle.

Put the gelatin in cold water for 5 min, or prepare by the instructions on the package. Put the egg yolks in a standing mixer and beat them until fluffy (or mix with a hand mixer), around 3 minutes. Put the sugar and water into a pan and bring to boil. Boil for 3 minutes, put off the heat and pour into the egg yolks in a thin stream while mixing constantly. Melt the gelatin and mix it in the egg yolk mixture. When the yolk mixture is not hot anymore add the mascarpone, vanilla extract and rose water, mix until combined. In a separate bowl mix the whipped cream until soft peaks and gently fold it into the mousse with a spatula.

Take the rhubarb disk out of the freezer, set it aside and prepare the mould. Pour half of the mousse in the mould, then place the rhubarb disk on top and the bigger sponge circle on that. Cover with the rest of the mousse making sure it fills all the mould without air bubbles. Place the second sponge circle on top and cover with a cling film. Place in the freezer overnight.

Bloom the gelatin in 80 g water, or prepare by the instructions on the package. Bring the sugar, glucose and 100 g water to a boil on a low-medium heat and boil for a minute or so, until the sugar is fully dissolved. Remove from the heat, add the condensed milk and gelatin and mix them in. Now add the chocolate and let it sit for 3 min. Mix everything together with an immersion blender. Be careful not to put air in the glaze, keep the immersion blender under the glaze. Tap on the counter a few times to reduce the bubbles and then strain it to remove the bubbles. Separate the glaze to 3 parts, use food coloring in gel or powder to color one part white, one pink and one blue. Now leave the glaze to cool to 33-35°C.

When the mirror glaze is cooled to 33-35°C, take the cake out of the freezer and the mould. Place a baking pan or a bowl upside down (something to put the cake on) on a bigger baking sheet, or something that will catch the leftover glaze. Place the cake, sponge side down, on the bowl or a baking pan. Now pour the white mirror glaze over the cake, then some blue and some pink. Gently scrape the top with a palette knife to blend the colors and make the top straight. The glaze will start setting pretty fast, so when it does, don't try to correct, or touch anything. Leave the leftover glaze to drip down, then remove the drips at the bottom with a knife, or scissors.

If you need help on how to glaze the cake you can refer to this video.

Leave the cake to thaw in the fridge for a few hours then cut and enjoy! :)