Preheat the oven to 180°C. Whisk the wet ingredients into a suitable container or jug. Line a high sided 8 inch cake tin, so the mixture doesn't leak, then tear the croissants up. Line the bottom of the cake tin with the crusty parts of the croissant in an even layer. Layer over some banana and dot over some chocolate chunks.
Repeat using a mix of the crust and the middle of the croissants and the remaining banana and chocolate, repeating till all the ingredients are used up. Finish with just croissants and dotted chocolate. Pour over the egg mix, pushing the croissants down slightly so they are coated and then with sprinkle over the sugar.
Place in the oven for about 25 minutes or until the cake is cooked and firmed up and the chocolate has melted.
