Preheat the oven to 350°F (175°C).
Mix together mochiko/rice flour, baking powder, and salt.
Melt the butter.
In a separate bowl, mix together eggs, sugar, coconut milk, milk, and vanilla bean paste until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing until fully incorporated.
Pour in 1/2 of the melted butter into your bowl before pouring in your other half and mix until fully combined.
Line baking pans with wet parchment paper. (Make sure to squeeze out the excess water to avoid a soggy cake.)
Separate about 200g of the batter into a bowl and mix it with the matcha powder to create a green batter.
Pour a thin layer of the plain vanilla batter into the bottom of a lined baking dish.
Sprinkle chocolate chips generously (follow your heart!).
Add another layer of the vanilla batter on top of the chocolate chips.
Drop dollops of the matcha batter on top.
Use a long toothpick or chopstick to gently swirl the matcha batter into the vanilla batter, creating a marble effect. Be careful not to overmix!
Bake for 50-55 minutes, or until the edges turn golden brown.
Remove from the oven and let it cool for 10-15 minutes before serving.
Enjoy your creation! Itadakimas!