Preheat the oven to 180°C. Put sunflower oil in a small pot along with rosemary, heat over a low flame for three minutes then set aside.
Mix together in a bowl soy drink and vinegar and let stand for 10 minutes.
Sift flour with baking soda, baking powder, cocoa and salt in a large bowl, add whole wheat flour and cinnamon and mix well.
Add the syrup, oil and grated orange zest to the mixture of milk and vinegar.
Add carefully liquids to dry ingredients using a spatula. Do not overmix, otherwise the cake will get dense and rubbery.
Pour the cake batter into a 20-22cm mold lined with parchment paper, level with a spatula.
Bake the cake for 20-25 minutes, a toothpick should come out clean when it's done. Remove the cake from the oven and from its mold, let it cool completely.
When the cake is cool remove baking paper then cut the cake horizontally into two, using a long knife.
Heat the jam in a small saucepan with the rum or orange juice just until they're slightly melted.
Spread this mixture over the two cake halves: this will give the cake more softness and humidity. Recompose the cake and let it rest at least 2 hours before serving.
Just before serving prepare a chocolate sauce to serve with the cake: melt dark chocolate with cooking cream. Mix well until smooth.
Note
In addition to chocolate sauce, you can pair the orange rosemary vegan chocolate cake with a dollop of whipped plant cream.