1. Preheat the oven to 180°C, gas mark 4. Grease a 21cm x 21cm cake tin and line with baking parchment. To make the cake, put the butter, cream, dark brown sugar, golden syrup and treacle in a saucepan and melt over a gentle heat until the sugar has dissolved.
2. Pour this mixture into a bowl, allow to cool for 5 minutes, then beat in the eggs one at a time. Fold in the flour, baking powder and spices until you have a smooth batter, then stir through the finely chopped stem ginger.
3. Tip into the cake tin and scatter over the roughly chopped stem ginger. Bake for 35–40 minutes, until a skewer inserted into the centre comes out clean.
4. If making the glaze, heat all the ingredients in a small saucepan with 4 tbsp water; simmer for 5 minutes, until reduced and syrupy. Prick holes all over the cake with a skewer or fork, then pour over the warm syrup.
5. Allow the cake to cool to room temperature in the tin set on a wire rack, slicing into squares to serve.