Place 1/2 cup water and the sugar in a large, heavy bottomed saucepan, and cook over low heat, without stirring, until the sugar is dissolved. Increase the heat to high and boil until the sugar turns a warm mahogany or caramel color, 3-5 minutes. Do not stir, but swirl the pan occasionally so the caramel cooks evenly.
Remove the caramel from the heat and carefully pour in the cream. The caramel is very hot, and the mixture will bubble up violently, then solidify. Don’t worry.
Return it to low heat and cook, stirring with a wooden spoon, until the caramel dissolves, 5-7 minutes. Add the vanilla. Pour into a container and refrigerate until very cold.
Something that is not suggested in the recipe is to strain the mixture first. Because the caramel solidifies and then you melt it down again, I definitely recommend this step.
Preheat the oven to 350 F. Roast the pecans on a baking sheet for 8-10 minutes, until crisp. Cool, chop, mix with the diced chocolate, and store in the refrigerator until ready to use.
Freeze the caramel mixture in an ice cream freezer according to the manufacturer’s directions. (It may take several batches). When it is frozen, add the cold chopped pecans and chocolate and mix in completely. Transfer to quart containers and store in the freezer until ready to serve.