Make The Cake

1. Preheat the oven to 170°C fan. Grease and line a 7-inch (18 cm) square cake tin with baking paper, leaving a little overhang to help lift out the cake later.
2. In a medium bowl, sift together the flour, black sesame powder, baking powder, bicarbonate of soda and salt. Black sesame powder can be slightly coarse depending on the brand. If some doesn’t pass through the sieve, gently press it through with the back of a spoon.
3. In a large mixing bowl, beat the softened butter and caster sugar together until pale and fluffy. This helps incorporate air into the batter for a lighter cake.
4. Add the vanilla extract and the eggs, one at a time, beating well after each addition. If the mixture looks slightly curdled, don’t worry; it should come together when you add the dry ingredients.
5. Add the dry ingredients in three additions, alternating with the buttermilk in two additions. Begin and end with the dry ingredients, mixing gently after each addition until just combined. Avoid over mixing the batter.
6. Transfer the batter to the prepared tin and spread it evenly into the corners.
7. (Optional) Soak a cake baking strip in water, squeeze out the excess, and wrap it around the outside of the cake tin. This helps the cake bake more evenly and reduces doming on the top.
8. Bake in a preheated oven at 170°C fan for around 35 minutes, or until a skewer inserted into the centre comes out clean. If the cake needs more time, continue baking and check again after a few minutes.
9. Leave the cake to cool in the tin for about 10–15 minutes, then lift it out using the baking paper and transfer it to a wire rack. Allow it to cool completely before decorating.

Make the Icing

1. Make the matcha icing: Mix the icing sugar and matcha powder into a bowl. Add the milk gradually, mixing until you have a thick but spreadable consistency. You may not need all the milk.
2. Make the white icing: Mix the icing sugar with the milk in a small bowl, adding the milk gradually until you have a thick but drizzleable consistency. If the icing is too thick, add a little more milk; if it is too runny, mix in a little extra icing sugar. If you’re using a piping bag to drizzle the icing, transfer it to a small piping bag. Alternatively, you can use a spoon to drizzle the icing over the matcha icing in an irregular pattern.

Decorate the Cake

1. Spread the matcha icing evenly over the cooled cake. Leave it for around 15–20 minutes so the surface can begin to set slightly.
2. Drizzle or spoon the white icing over the matcha icing in your preferred pattern, depending on the look you want to achieve.
3. While the icing is still slightly tacky, arrange the gummy eyeballs and Halloween sprinkles over the top. If the icing has already set, use a little extra icing to secure the decorations.
4. Once the icing has set enough to handle, cut the cake into nine squares and serve.