Preheat oven to 185oC / 170oC Fan.
Grease and line a 22cm square cake tin.
Put all the cake ingredients into a large bowl and mix together using a fork.
Spoon the mixture into the cake tin and bake for 30-35 minutes.
Before removing the cake from the oven test it is fully cooked on the inside by sticking a skewer or small knife into the middle. If it comes out clean the cake is ready. If there is still some cake mixture in it, leave to cook for a few more minutes and then check again.
Once cooked leave to cool in the tin on a wire rack for 20 minutes and then remove from the cake tin and place back onto to the wire to cool completely.
Cut the cake in half then portion each half into 8 pieces.
Place the bag of chocolate chip into a small jug of hot water. Allow to melt then cut the corner and drizzle over each bar and place into the fridge until the chocolate is set.