1. Preheat the oven to 250F. Spray two 15 x 10 1/2-inch baking pans lightly with cooking pray.
2. Melt the butter in a medium saucepan over low heat. Add the honey, brown sugar and salt. Cook the mixture, stirring constantly, for 2 minutes. Remove from the heat. Add the baking soda and mix well.
3. Combine the popcorn, cereal, cashews and peanuts in a large bowl and toss until mixed. Add the honey mixture and toss to mix (careful, it will be hot).
4. Spoon equal portions of the popcorn mixture into the prepared baking pans. Bake, stirring occasionally, until golden brown, 35 to 45 minutes. Store in airtight containers for up to 2 weeks.
Tip
For individual servings for trick-or-treaters or lunch boxes, spoon the mix into sandwich-size plastic bags and seal.