Preheat the oven to 250F and put the popcorn in a big bowl.
In a medium saucepan, combine the brown sugar, corn syrup, butter, molasses and salt and bring to a boil over medium heat. Reduce the heat and boil without stirring, swirling the pan occasionally, for 4 minutes. Remove from heat and stir in the baking soda and vanilla - it will foam up at first. Stir in the cinnamon and ginger and quickly pour over the popcorn; stir with a heatproof spatula or tongs to coat well.
Spread out onto a large rimmed baking sheet and bake for 30 minutes, stirring once or twice. Cool and break apart.