Preheat oven to 350°F/177°C.
Prepare a 8" by 8" square baking container by lining it with parchment paper.
In a large bowl, add the eggs, coconut milk, almond milk, coconut sugar (or sweetener), vanilla and beat with a whisk until slightly frothy.
Add in the black sesame powder, glutinous rice flour (mochiko), charcoal powder (if using), and baking powder.
Give the mixture a stir with a spatula until everything is incorporated.
Transfer the batter into the prepared baking container and smooth out the top. Add some black sesame seeds as a garnish on top if you wish.
Gently tap the baking container a few times on the table to release any trapped air bubbles.
Bake for 35-40 minutes at 350°F/177°C or until a toothpick inserted comes out clean. Top will be slightly brown.
Remove from oven and let cool over a cooling rack.
Cut into squares using a sharp serrated knife and serve at room temperature.
Black sesame mochi may be stored at room temperature in an airtight container for up to 2 days.