Prepare the Cake Batter:

1. Preheat your oven to 350°F (175°C). Grease or line a 7-inch round cake pan with parchment paper.
2. In a large bowl, sieve and whisk together the dry ingredients: flour, cocoa powder, date sugar, baking powder, and salt.
3. In another bowl, mix the wet ingredients: plant-based milk, orange juice, nut butter, and vanilla extract.
4. Gradually combine the wet and dry ingredients, mixing until smooth and lump-free. Avoid overmixing.
5. Pour the batter into the prepared pans and bake for 35 minutes, or until a toothpick inserted in the center comes out clean.
6. Let the cake cool in the pan for 10 minutes before transferring to a wire rack to cool completely.

Make the Chocolate-Orange Mousse:

1. Blend the silken tofu, orange juice and zest in a food processor until smooth.
2. Melt the chocolate in a double boiler or the microwave.
3. Add the melted chocolate to the silken tofdu mixture and quickly bend until creamy and well combined.

Assemble the Cake:

1. Cut the cooled sponge cake in half horizontally. Place the bottom half back in the tin and pour the chocolate-orange mousse over it. 
2. Smooth out and place in the fridge for 1.5 to 2 hours.
3. Then place the top half on top.

Prepare the Ganache:

1. Heat the plant milk in a saucepan over a low heat. When it starts to simmer, add the coarsely chopped chocolate,
2. Remove the pan from the heat and allow the chocolate to melt for 2-5 minutes. Then stir until smooth.
3. Carefully remove the cake from the tin and pour the ganache layer over the cake.