Combine the popcorn, mixed nuts, salt, paprika and cayenne pepper in large serving bowl.
Line a large baking sheet with aluminum foil and coat with nonstick spray.
Melt the butter in a heavy-bottomed saucepan over medium-high heat. Pour in the maple syrup and continue cooking until the mixture reads 275 degrees F on a candy thermometer, about 15 minutes.
Carefully pour the mixture over the popcorn and nuts. Toss, using a spoon that has been coated in nonstick spray, to coat the popcorn evenly with syrup. Allow the popcorn to cool before serving.