In a medium-size saucepan, combine the almond milk, coconut milk, and maple syrup. Add the cornstarch, the agar, and the "Almond Matcha" powder, and whisk thoroughly.
Heat over medium heat, whisking constantly until it thickens (usually just before boiling). Once it has thickened, remove from heat, add the vanilla extract, and whisk again.
Pour the preparation into a cake pan. Let the Blackberry Matcha custard cool a bit at room temperature before transferring to the refrigerator. Refrigerate for at least 8 hours, the Blackberry Matcha custard will thicken and slightly harden.
To serve, run a knife along the edges of the cake mold, cover with a plate and flip it. Serve fresh, topped with blackberries!