In large mixing bowl, combine popcorn, almonds, cashews and pecans.
In saucepan, combine butter, sugar, maple syrup, brown rice syrup, 1/4 cup water, salt and cinnamon; bring to boil over medium heat, stirring occasionally. Cook until mixture reaches hard crack stage (295°F).
Slowly pour syrup in thin stream over popcorn mixture. Toss gently to coat evenly. Let cool; break into large chunks.