In heavy saucepan, over low heat, melt butterscotch chips with 1/3 cup sweetened condensed milk. Remove from heat. Stir in vinegar. Drop by small spoonfuls onto wax paper lined baking sheets. Arrange 3 pecans on each butterscotch drop.
In large heavy saucepan, over low heat, melt chocolate chips with remaining sweetened condensed milk, and vanilla. Remove from heat.
Hold chocolate mixture over hot water. Drop chocolate by heaping spoonfuls over pecan clusters. Chill 2 hours, or until firm. Store covered in refrigerator. Makes about 5 dozen candies.