1kg forced rhubarb, trimmed, washed and cut into 2.5cm pieces
Place the onion, cinnamon, star anise and vinegar in a large, heavy-based pan and bring to the boil. Reduce the heat and simmer for 10 minutes.
Add the orange zest and juice, raisins, both gingers and sugar, and stir until the sugar dissolves. Simmer for 15 minutes, until it is a thick syrup. Add the rhubarb and cook gently for about 10 minutes.
Pour into sterilised jars, cool, then seal and store in the fridge for up to 5 weeks.