In a bowl, mix the flour with all the other ingredients up to and including the red currant jelly. Transfer the mixture to the prepared tin.
Place the tin in the lower half of a cold oven and bake for approx. 35 mins at 180°C. Remove from the oven, allow to cool slightly on a cooling rack.
Warm the butter in a pan, remove the pan from the heat. Chop the chocolate, add to the pan, melt. Stir in the icing sugar, stir until smooth, drizzle over the gingerbread, leave to cool. Cut the gingerbread into 16 squares.