Combine the following in a saucepan:
1 cup white sugar
1 cup brown sugar
1 cup butter (must be actual butter)
1 cup agave nectar
1 cup heavy cream (plus 1 more cup of cream to be added once it is boiling)
Cook together until it boils. Once it boils, slowly add 1 additional cup of cream. Turn heat down so that it boils gently, stirring every three minutes until it is a caramel-y color, about 30 minutes. If you stir it constantly or cook it for too long, the caramels will be too hard.
After 30 minutes at a rolling boil, remove from heat and stir in 2 teaspoons of good quality vanilla. Pour in a buttered loaf pan. Let set and cut into squares. I have had to make these several time to get them to be just the right texture. Experiment a bit before you plan to give them as a gift.
The type of stove you have will effect the cooking time of the caramels. I have a gas stove and it takes 30 minutes. Try cooking them for 30 minutes the first time and you will know whether that is too much or not enough. If it is too much the caramels will be too hard (like lozenges) and if it is not enough they will not set up enough to cut and serve (except in a spoon). You can reheat those that are too soft and cook them a bit longer in an effort to reach the proper caramel consistency. These are not the easiest things to get right but once you do, they are the BEST!