Combine the cocoa powder, flour, sugar and ginger in a microwave-safe mug with a pinch of salt until smooth. Mix together the melted Arla LactoFREE spreadable butter and the ginger syrup in a small jug. Pour into the flour mixture along with the chopped ginger and chocolate. Stir until just combined, then microwave on high for 60-80 seconds – the top should be cooked and set. Leave to stand for a couple of minutes to cool. Grate over some extra chocolate to serve, if you like.