Prepare the popcorn without salt, in the usual way, and put it in a bowl.
Place the corn syrup, butter, sugar, and salt in a pot on the fire, stirring constantly, until the sauce boils.
Remove the caramel sauce from the heat, place the vanilla and bicarbonate of soda on top, and the sauce will be fizzed.
Immediately place the sauce on top of the popcorn, stirring well, until all the popcorn is covered with caramel.
Preheat the oven to a temperature of one hundred and twenty degrees Celsius.
Prepare two molds, and grease them with a little oil.
Distribute the popcorn in the two molds, and bake it in the oven for only one hour, and the two molds are taken out every quarter of an hour, and stir the popcorn.