Preheat oven to 250 F. Line a rimmed baking sheet with parchment paper and spray with cooking spray.

Heat the oil in a large Dutch oven set over medium-high heat. Add the popcorn kernels and cover. Cook, shaking the pan frequently, for about 4 minutes, or until the popping almost completely stops. Remove the pan from the heat and when the popping stops, remove the cover and add the almonds.

In a medium saucepan, combine the brown sugar, corn syrup, butter and salt. Bring to a boil over medium heat, then continue cooking for 3 minutes, stirring occasionally. Remove the pan from the heat and mix in the peanut butter and vanilla. Drizzle over the popcorn and use a rubber spatula to toss to coat.

Spread the popcorn on the prepared pan. Bake for 1 hour, stirring every 15 minutes. Let cool completely before serving.