Place cold vegan butter in a large mixing bowl and using an electric hand mixer, beat for 2 minutes. Gradually add all the stevia and corn starch and beat until light and fluffy.
Place in refrigerator until ready to use.
For the cake batter:
Toast the black sesame seeds in a frying pan over medium low heat for 5 minutes or until fragrant. Set aside to cool.
Place the toasted black sesame seeds in a food processor, ground until fine meal.
Heat up the rice milk, vegan butter and rapadura sugar in a small pot for 2 minutes or until the vegan butter and sugar have melted, stir and combine well.
Sift all the dry ingredients except desiccated coconut and the black sesame meal into another large mixing bowl, whisk and combine well.
Then add in the black sesame meal and desiccated coconut and whisk and combine. Make a well in the centre of the mixing bowl.
Gradually pour the wet ingredients mixture prepare in step 4 and the vegan egg replacer mixture into the well and use a spatula to mix briefly. Then whisk until well combined.
For cooking the cake:
Pre-heat fan-forced oven to 160C or 320F.
Grease the cake tin with some vegan butter and line the bottom of the cake tin with baking paper.
Pour the cake batter into the cake tin and spread evenly with a spatula.
Bake the cake for 50 minutes or until tooth pick comes out clean.
Cool in cake tin for 10 minutes, then remove and place the cake on a cooling rack.
For frosting the cake:
Let the cake cool completely before frosting with an icing spatula.
Garnish with the pistachio nuts and black sesame seeds on top of the frosting. Slice into 16 square pieces and serve.