Preheat the oven to 175°C. Line a 30 x 11 x 9 cm loaf pan with parchment paper.
Blend the bananas, orange juice, and melted vegan butter until smooth.
Combine all the dry ingredients in the bowl of a stand mixer fitted with the paddle attachment. Add the banana purée and beat until smooth. Fold in the chopped candied orange and mix well.
Pour the batter into the prepared pan and spread it evenly with a spatula.
Bake for 40 to 45 minutes, or until a toothpick inserted into the center comes out clean.
Transfer the cake to a wire rack and let it cool completely.
Trim the top, then cut the cake into four layers, each about 1 cm thick. Refrigerate until needed.
Chocolate Ganache
Heat the whipping cream in a saucepan until it just begins to boil. Remove from the heat.
Pour it over the chocolate, then blend with an immersion blender until smooth and glossy. Cover and keep warm.
Coffee Syrup
In a saucepan, bring the water and sugar to a boil. Remove from the heat, stir in the coffee powder, and set aside.
Cake Assembly
Lightly grease the loaf pan, then line it with plastic wrap.
Place the first banana cake layer in the bottom of the pan and soak it with coffee syrup. Spread 1/3 of the chocolate ganache evenly over the top.
Add the second banana cake layer, soak it with coffee syrup, and spread over the next third of the chocolate ganache.
Add the third banana cake layer, soak it with coffee syrup, then spread over the remaining chocolate ganache.
Top with the final banana cake layer, soak it with coffee syrup, then press gently to level the surface.
Freeze for at least 3 hours.
Yellow-Green Chocolate Glaze
Melt the white chocolate over a double boiler until it reaches about 50°C.
Heat the vegan cream to just below a boil, then add the food coloring.
Blend the melted white chocolate with the hot cream using an immersion blender until smooth and glossy.
Invert the fully assembled, well-chilled cake onto a wire rack. Remove the plastic wrap.
Reheat the glaze to 35°C, then pour it evenly over the cake. Remove any excess glaze with an offset spatula to smooth the surface.
Refrigerate the glazed cake for 10 minutes to set.
Vegan Italian Meringue
Make a vegan Italian meringue: whip the potato protein with the water and xanthan gum, then stream in the cooked sugar syrup to stabilize it.
Use a Saint-Honoré tip to pipe the vegan meringue decoration. Watch the video for the proper piping technique.