1. Preheat oven to 200 degrees Fahrenheit. Grease a large piece of foil and set aside. Remove all unpopped kernels from the popped popcorn.
2. In a 17-inch x 12-inch baking pan, combine popcorn, pecans and almonds. Place popcorn mixture in warm oven.
3. Using margarine or butter, grease the inside of a heavy two-quart saucepan. In the saucepan, combine sugar, remaining margarine or butter, and corn syrup. Cook and stir over medium-high heat until mixture boils.
4. Clip a candy thermometer to the pan; reduce heat to medium. Continue boiling at a moderate, steady rate, stirring often, until thermometer registers 280 degrees Fahrenheit, when the caramel reaches the soft-crack stage (about 15 minutes). Remove saucepan from heat. Stir in vanilla.
5. Remove popcorn mixture from oven. Carefully pour caramel mixture over warm popcorn mixture; using a wooden spoon, stir gently to coat. Spread popcorn mixture on prepared foil to cool. Using two forks, break popcorn mixture into clusters.