1. Preheat the oven to 170C/150C/Gas 3. Line a tin (preferably 30x20cm/12x8in) with baking paper.
2. Sieve the flour into a large bowl along with the ginger, cinnamon & mixed spice and gently mix them together to combine.
3. Place the butter, the brown sugar, the syrups (Lyle's Golden Syrup and stem ginger syrup) & black treacle into a saucepan. Melt everything together over a gentle heat.
4. Remove the melted mixture from the heat and whisk in the milk, the bicarbonate of soda and the eggs. Gradually add the contents of the saucepan to the flour, making sure everything is well combined. You will end up with a wet, pourable batter. Stir through the chopped stem ginger (if using).
5. Bake in the oven for between 45 minutes and an hour. When the gingerbread cake is springy to touch, it will be done.
6. Cool in the tin for half an hour and then turn out onto a wire rack. Dust with icing sugar to finish. If you can, keep for a few days before eating – the gingerbread cake will get stickier as it matures.