Combine sugar, butter, corn syrup, water and salt in a large saucepan over medium heat. You're going to bring the candy to the hard ball stage at 265-275 degrees. If you don't have a thermometer, it's okay. Drip the candy into a small glass of cold water. If the candy forms a very hard yet slightly pliable ball, there you go. Watch this mixture CLOSELY, so that it doesn't boil over.
While the candy cooks, pop both bags of popcorn and spread it (plus almonds if you choose) onto one large or two small cookie sheets. Put the popcorn in your oven set on it's lowest temp. (this keeps the popcorn hot so the candy will coat better).
When your candy has reached the hard ball stage, add the vanilla.
Pull the popcorn from the oven and, working quickly, pour the candy over the popcorn in thin streams. Mix the popcorn so that each kernel is coated with candy. Put the popcorn back into the oven for five more minutes, then stir once again. This will help coat each kernel. Repeat this step once more if necessary to get it all coated.
Pour popcorn onto a large sheet of wax paper to cool. Spread it out but be careful, it's HOT. When it's cooled, break it up and immediately put it into a tightly sealed container as it stales easily.