Mix everything everything except vanilla in a medium saucepan over medium heat. Bring to a rolling boil. Cook until mixture reaches firm ball stage (245-250 °F on a candy thermometer), stirring constantly. Remove from heat and add vanilla.
Continue to stir mixture as it cools, until the margarine stays in suspension (it’s no longer floating on the surface). Dip apples at this point. (If you want “add ons”–nuts, coconut, cookie crumbs–roll immediately while caramel is still warm/sticky.) If your kitchen is warm, store dipped apples in fridge. For ice cream topping, either use immediately or reheat in double boiler until loose enough to pour.
Or allow mixture to cool until it’s handle-able. Grease hands and pull caramel until it takes on a lighter color and then roll into small bites.
Special note–do NOT crank burner to high and try to go faster or mixture will over expand and threaten to overflow pot.
I know pinch isn’t a quantified measurement, but it was just what I grabbed between my fingertips–a “small” pinch vs a “heavy” pinch, kwim? 1/8 tsp, maybe? 1/4 tsp, max. It’s not “salty” at all, just enough salt to bring out flavors.