In an airpopper, pop popcorn kernels and place in a large bowl. Preheat oven to 250F and line two baking sheets with parchment paper. Set aside.
In a medium saucepan over medium heat, melt butter. Whisk in sugar, agave, spices, and salt until smooth. Cook caramel over medium heat, stirring occasionally until sugar is dissolved and caramel is bubbly and thickened, about 5 minutes. Remove caramel from heat and whisk in vanilla and baking soda.
Immediately pour hot caramel over popcorn and gently stir until popcorn is evenly coated. Spread popcorn evenly on two prepared baking sheets. Bake popcorn at 250F 1 hour until popcorn is crispy and caramel is golden. Drizzle popcorn with melted white chocolate and let stand 30 minutes to set before breaking into pieces. Enjoy!