Source: Boy Scouts of America
4 quarts popped popcorn
1 1/2 cups granulated sugar
1/2 cup light corn syrup
2 tablespoons butter
1/2 teaspoon salt
1/4 teaspoon cream of tartar
3 to 4 tablespoons gelatin powder, your choice of flavor
1 teaspoon baking soda
Preheat oven to 250 degrees F. Place popcorn in a large 4-inch deep buttered baking pan. Keep warm in the oven.
Line 2 cookie sheets with wax paper and butter the paper.
In a large saucepan, combine sugar, corn syrup, butter, salt and cream of tartar. Bring to a boil, stirring constantly. Cook without stirring until mixture reads 250 degrees F on a candy thermometer. Stir in gelatin powder and cook another minute until it reaches 260 degrees F.
Remove from heat, then stir in baking soda quickly. Remove popcorn from the oven. Pour syrup over top of popcorn while syrup is still foamy. Gently mix to coat popcorn. Bake at 200 degrees F for 1 hour, stirring 2 to 3 times. Turn onto buttered paper. Cool completely and store.