Step 1

Preheat the oven to 200 degrees F. Grease or butter two large, rimmed baking pans. Combine the popcorn, peanuts, pistachios and sesame seeds in a very large bowl or roasting pan.

Step 2

Melt the butter in a medium saucepan over medium heat. Add the brown sugar, corn syrup, peanut butter and salt. Bring to a boil, stirring constantly, then cook until the mixture is completely emulsified and there is no visible melted butter around the edge of the pan, 1 to 2 minutes. Remove from the heat and stir in the vanilla and baking soda. (The mixture will puff up.)

Step 3

Pour the mixture evenly over the popcorn mixture and toss well to coat. Divide the popcorn between the two prepared pans, spreading in an even layer. Bake the popcorn for 1 hour, stirring every 15 minutes and rotating the pans so it cooks evenly. Let cool in the pans, about 20 minutes. Break into pieces to serve.