Line 3 x 12 hole muffin pans with paper patty cases.
Combine butter, chocolate, sugar and water in a large pan; stir over a low heat until chocolate is melted and sugar is dissolved. Transfer mixture to a large bowl then cool for 15 minutes.
Whisk in flours, vanilla and eggs until combined. Pour mixture into a large measuring jug then divide mixture among paper patty cases, do not over-fill.
Cook in a slow oven, 150c, for about 30 minutes, or until cooked when tested. Transfer to a wire rack to cool.
To make the icing, beat the butter and sugar in a medium bowl with an electric mixer until light and fluffy. Beat in icing sugar and enough milk to form a spreading consistency.
Spread icing over cakes; top with halved Jersey Caramels.