Preheat your oven to 180°C. Line your traybake tin with baking paper carefully. This helps the cake release easily after baking. Greasing the corners also prevents sticking and keeps the edges neat.

Place instant coffee into a small cup. Add hot water and stir well. Let the coffee cool slightly before adding it to the batter. This gives the cake a deep coffee flavor.

Add softened butter and caster sugar into a large bowl. Beat until light and fluffy. The mixture should look pale and creamy. This step helps create a soft and airy cake texture.

Crack the eggs into the bowl one at a time. Beat well after each addition. Adding eggs slowly prevents the batter from splitting and keeps the mixture smooth and creamy.

Sift the flour and baking powder into the bowl. Fold gently using a spatula. Do not overmix the batter. Gentle mixing keeps the traybake soft and fluffy after baking.

Pour the cooled coffee mixture and vanilla extract into the batter. Add milk too. Stir carefully until everything combines smoothly. The batter should look silky and smell wonderfully rich and sweet.

Pour the batter into the prepared tray evenly. Bake for about 30 minutes. The cake should feel springy when touched lightly. A skewer inserted in the center should come out clean.

Remove the cake from the oven carefully. Let it cool inside the tin for ten minutes. After that, place it on a cooling rack until fully cooled before frosting.

Mix instant coffee with hot water in a small bowl. Beat butter until smooth. Add powdered sugar, cocoa powder, coffee mixture and milk. Beat everything together until creamy and fluffy.

Spread the frosting evenly across the cooled cake. Use a spatula for smooth edges. Decorate with chocolate curls, cocoa powder or chopped nuts for extra flavor and a beautiful finish.