Preheat oven to 356°F/180C. Grease two 8inch cake tins with vegan butter.
Add avocado flesh to a food processor, then fold in eggs, vanilla and water. Blend all of the ingredients until smooth.
Add the sugar, cocoa powder, rice flour, melted chocolate, pecans and chocolate chips. Stir together all of the ingredients, fold in the baking soda and stir until just combined
Transfer the mixture to your prepared tins, sprinkle with sea salt flakes and bake in the oven for 20-25 minutes, or until a toothpick inserted comes out clean.
Allow to cool completely before removing from the tins and placing on a cooling rack.
Meanwhile, prepare the buttercream: ,mix together vegan butter and icing sugar, gently pour in the coffee and beat the mixture until creamy and smooth. Keep in the fridge until ready to use.
Spread the buttercream over one of the cakes and place the remaining cake upside-down on top.
For the glaze: melt the chocolate in a heatproof bowl over a pan of boiling water. Then mix in 1 tbsp of water and allow to cool slightly.
Pour the chocolate glaze over the brownie cake, coating evenly all sides, and decorate the edges with chopped pecans and almonds.
Top with halved pecans, allow to set and serve at room temperature or slightly chilled. Store in the fridge in an airtight container for up to 2 days.