Using an popcorn air popper, pop the kernels until cooked. Let cool slightly. Spread in thin layers on baking sheets; set aside.

In a 3-qt. saucepan, combine challenge unsalted, brown sugar, and corn syrup. Using a candy thermometer, boil to a Hard-Ball Stage.

Remove from heat, and stir in baking soda. Quickly pour on top of popcorn & mix gently until covered.

Bake at 250°F, stirring every 15 minutes, for 45 minutes. Cool completely.

Melt chocolates in microwave-safe bowls. Drizzle chocolate over popcorn, alternating between both white & milk chocolate. Allow to cool & harden for at least 15 minutes. Break popcorn apart, and store tightly covered.