3 packages (3.5 ounce) microwave popcorn, popped
2 1/4 cups brown sugar
1 cup corn syrup
1 cup butter
5 ounces sweetened condensed milk

Place popcorn in a large bowl. Shake and toss bowl to make unpopped kernels go to the bottom; discard. In a sauce pan over medium-high heat, cook brown sugar, corn syrup and butter together, stirring constantly. Heat to 270°-290°F till a small amount of syrup dropped into cold water forms hard but pliable threads. Remove from heat and carefully pour in the can of condensed milk; stir till smooth. Pour 1/4 of the caramel at a time over the popcorn, stirring till all of the popcorn is covered. Cool at least 10 minutes before serving.