Preheat oven to 350 degrees Fahrenheit.
Mix together the coconut oil and chickpea brine with a hand mixer. Add the cake mix and beat until smooth.
Combine the cashew milk and 1/2 teaspoon matcha powder in a high speed blender and blend until smooth.
Add the cashews and blend until smooth-it will be a semi-thick liquid. Pour into a medium sized mixing bowl and set aside.
In a glass bowl, melt the cacao butter in 20 second intervals in the microwave. Once completely melted, add it to the cashew and matcha mixture. Blend with a hand mixer until smooth.
Add the vanilla extract and another 1/2 teaspoon matcha powder and blend until smooth.
Add the powdered sugar in 1/4 cup portions, blending between each. Keep going until the frosting is the right consistency, about 1 and 3/4 cups to 2.
Frost the cookies. Pour a 1/2 tablespoon frosting on each cookie. Spread it out towards the edge of the cookie. The frosting should be thick enough that it sets but liquid enough that it forms a smooth glaze.
*Refined coconut oil makes sure the cookies don't taste like coconut.
You can use store bought cashew butter if you like, but it will be a lot thicker. Be prepared to add less powdered sugar or more cashew milk.
The frosting makes about 1 and 1/4 cups.