In a heavy saucepan, combine the butter, brown sugar, corn syrup and milk; bring to a boil over medium-high heat.
Cook and stir until a candy thermometer reads 248 degrees (firm ball stage) about 30-40 minutes and for a softer caramel cook just to a few less degrees.
Remove from heat; stir in vanilla.
Dip each apple into hot caramel mixture; turn to coat.
Holding by the stick, sprinkle with nuts or whatever you desire while the caramel is still warm (work quickly the caramel sets up fast).
Set on generously buttered wax paper to cool (make certain to generously butter the paper).
You can make tons of varieties on this recipe. Just roll the apples in after rolling them in the caramel. Mini M&M's, nuts, chocolate, cereal or just about anything just make certain to roll while the caramel is still soft on the apples.