Step 1

Preheat oven to 170C. Grease an 18cm x 27cm slice tin and line with baking paper, allowing a 3cm overhang.

Step 2

In a small saucepan, melt butter with brown sugar and golden syrup. Set aside to cool slightly. In a large bowl, whisk together flour, baking powder, bicarb soda and cinnamon. Whisk in melted butter mixture, eggs and vanilla. Combine milk and vinegar in a small jug and allow to sit for 1 minute. Add to cake better and whisk until smooth.

Step 3

Pour into prepared tin and bake for 25 minutes. Remove cake from tin and allow to cool on a rack.

Step 4

To make icing, beat together all ingredients until smooth. Pour icing over cake and spread out evenly.