In a small pot, heat the coconut milk until just boiling (or microwave for about 2 minutes).
Pour this mixture over the chopped chocolate and stir until the chocolate is melted.
Add the agave syrup or powdered sugar and beat with a hand mixer until smooth.
Remove 1/3 cup of the chocolate frosting (to use in the chocolate mousse). Let cool remaining frosting until thickened into a spreadable frosting.
Using a hand mixer, beat the vegan cream cheese, non-dairy whipping cream, powdered sugar, and vanilla until creamy. Pour in reserved 1/3 cup frosting and continue beating until thick and stiff peaks form. (If the frosting became to firm in the meantime, slightly heat up again until melted).
In a small pot, thaw frozen raspberries over medium-high heat, stirring occasionally. Mash with a spoon.
In a small cup, dissolve cornstarch in 2 tbsp water. Stir into the raspberries along with the sugar and lemon juice. Bring to a simmer, stirring constantly, and cook for 1-2 minutes until thickened. Set aside to cool. (It will thicken up even more when cooled).
Preheat the oven to 350°F (175°C). Grease and line three 8-inch (3x20cm) cake pans.*
Stir the apple cider vinegar into the non-dairy milk and set aside to curdle into vegan buttermilk.
In a small pot over medium heat, slowly melt the vegan butter. Stir in coffee granules and vanilla extract. Set aside to cool slightly.
Sift the flour, cocoa powder, sugar, baking powder, baking soda, and salt into a bowl and mix to combine.
Pour the vegan buttermilk and soft butter mixture over the flour mixture. Also, add the apple sauce and stir just until combined and no large lumps remain (please do not overmix). (Adjust sugar to your desired taste).
Fill the batter into the prepared cake pans and bake for about 30 minutes, or until a skewer inserted into the center of the cake comes out almost clean. Then let cool completely. (If you want a moist chocolate cake, make sure not to overbake it.)
Assemble the Cake:
Remove the frosting from the fridge and mix until creamy.
Place one cake layer on a serving plate. Spread about 1/2 of the raspberry jam over the cake. Then spread 1/2 of the chocolate mousse over it. Top with the next layer, and repeat this process. Place the third layer on top and spread the chocolate frosting all over your cake.
Decorate with fresh berries and chopped chocolate if you like and enjoy!