Prepare 1- ¼ sheet pan with pan grease & parchment paper liner for the chocolate cake recipe then prepare according to the instructions on that post
Meanwhile line your large loaf pan with plastic wrap allowing some of it to drape over the sides for easy removal later.
Once the cake is cooled - cut it to fit in the bottom of the loaf pan & reserve another layer for the top, then cut the remaining cake into chunks for the middle layer - reserve everything in the refrigerator while you prepare the first mousse recipe
Prepare the vanilla mousse by combining the vanilla bean pod (scraped of its seeds) with the plant milk and the agar in a medium sauce pot & bring to a boil and then remove the vanilla bean pod. *If you are using extract instead you will add that later
Pour the hot milk mixture over the finely chopped vegan white chocolate in a large mixing bowl & whisk smooth. Let it cool slightly but not too cold or it will set too much *see video visual for clarification
Next prepare the meringue with the aquafaba by whipping it with the cream of tartar, once it starts to gain strength & gets thicker & glossy add the sugar very slowly but keep whipping until it is firm glossy stiff peaks.
Next whip the vegan whipping cream of your choice to medium peaks and fold it quickly into the white chocolate mousse base, then gently fold in the aquafaba.
Pour the mousse into the prepared loaf pan with the chocolate cake & sprinkle the reserved chocolate cake chunks over top
Refrigerate to set while you prepare the chocolate mousse layer
Make the chocolate mousse by melting the vegan semi sweet chocolate over a double boiler or in the microwave. Add the hot coffee & whisk smooth allow it to cool slightly
Whip the vegan whipped cream to medium peaks & set aside
Next prepare the aquafaba by whipping in a high speed balloon whip stand mixer with the cream of tartar until thick & glossy, slowly add the sugar
Once the mousse base it cool enough to not melt the whipped cream, fold in the whipped cream, then fold in the whipped aquafaba.
Immediately pour over the vanilla bean mousse layer & cake chunks in the pan
Top with the remaining cake layer and refrigerate everything overnight or freeze for 4 hours to set completely
Unmold the cake then glaze the top with ganache icing & a decoration of white chocolate striping if desired