Preheat the oven to 160°C (without fan) and line the 2 LB (900g) loaf tin with baking paper.
Finely chop the chocolate bar into uneven small chocolate chunks, slightly smaller than the size of a pea.
Mash the banana, zest and juice. Don't mash it too much, it will get too runny.
Sift the flour, salt, baking powder and bicarbonate soda into a mixing bowl. Stir to combine.
Add the remaining ingredients (except for the chopped chocolate) into the mixing bowl. Beat until thoroughly mixed. It takes less than 1 minute. For me, it's 40 to 45 seconds.
Gently stir in the chocolate chips coated in flour.
Quickly transfer the batter to the prepared loaf tin. Level the top.
Bake at 160°C for 60 minutes.
To test if the cake is done, insert a skewer into the cake. The skewer should come out clean, and the cake slightly shrinks away from the tin.
Optional: Once you remove the cake from the oven, sprinkle some chocolate over the top of the hot cake. I like to use chocolate chips as they don't lose their shape even when melted.
Let the loaf cool down for 10 minutes in the tin, then remove from the tin and continue cooling down on the wire rack.