To make homemade caramel popcorn, bring 2 cups brown sugar, 1 cup butter, 1/2 corn syrup and 1 teaspoon salt to the boil in a saucepan. Stir in 1 teaspoon baking soda, then pour over prepared popcorn and bake for 1 hour at 200 degrees Fahrenheit, stirring every 15 minutes.
Preheat the oven to 250 degrees Fahrenheit and line a baking sheet with parchment paper. Pop the corn kernels ahead of time, preparing 8 cups of popcorn. Place the popcorn in a large mixing bowl and set aside.
For the caramel sauce, make sure the mixture boils on the stove for 4 to 5 minutes for the right consistency. Let it come to a boil over medium heat to avoid the sugar and syrup burning. Remove the caramel sauce from the heat before stirring in the baking soda, which causes it to bubble up. You can also stir in a teaspoon or so of vanilla extract for additional flavor. Stir until the sauce becomes thick and glossy.
When pouring the caramel sauce over the popcorn, stir the popcorn consistently until all of the popcorn is evenly coated. Spread the coated popcorn onto the lined baking sheet in a single layer. Use two baking sheets if necessary. Place the caramel popcorn in the oven for one hour and stir the popcorn every 15 minutes, making sure to break up any clumps. Cool the caramel popcorn on wax paper before serving.