From the Cook’s Illustrated bulletin board:
Here is my Mom’s caramel apple recipe:
1 C. sugar
3/4 C. dark corn syrup
1 C. light cream
2 Tbls. Butter
1 tps. Vanilla
5-6 medium size crisp, tart apples. Cleaned, dried, with a stick inserted
Combine all ingredients except the vanilla. Stir over low heat until sugar dissolves, then cook, without stirring to firm ball stage. (245° F–250° F, sugar concentration: 87%)
Take off heat, stir in vanilla and dip apples.
Cool on a sheet of parchment or buttered foil. (I used that non-stick foil and it released the caramel without a problem.)