Sticky stem ginger cake with lemon icing

INGREDIENTS

• 225g self-raising flour
• 1 tsp bicarbonate of soda
• 1 tbsp ground ginger
• 1 tsp ground cinnamon
• 1 tsp ground mixed spice
• 115g butter , cut into cubes, plus extra for greasing
• 115g dark muscovado sugar
• 115g black treacle
• 115g golden syrup
• 250ml whole milk
• 85g drained stem ginger , finely grated
• 1 egg
• 50g icing sugar, sifted
• 1 tsp finely grated lemon zest
• 1 tbsp lemon juice