Line an 8x8" square pan with parchment paper and preheat your oven to 175°C (350°F).
Add the loose chai to a saucepan with the oat milk and water. If using teabags, cut them open and empty the contents into the saucepan. Bring the mixture to a simmer on medium heat and continue to heat for 5 minutes. Remove the saucepan from the hob and allow it to steep for another 5 minutes before passing through a sieve to remove the loose tea.
Add the chai mixture to a large bowl along with the cashew butter, maple syrup, apple sauce, and vanilla extract. Whisk until evenly mixed.
Add the remaining ingredients to the bowl and gently fold them in using a spatula. Be careful not to over-mix, a few pockets of flour visible in the batter is ok.
Add the cake batter to the prepared loaf pan and bake for 30 minutes. Check the cake is ready by inserting a knife or toothpick into it, which should come out clean. Allow the cake to cool in the pan for about 20 minutes before transferring it to a cooling rack.
Meanwhile, make the vegan cream cheese frosting if you're using it. Once the cake has cooled, frost as desired.