Velveeta cheese (3/4 of a 16 oz. block) cut into half-inch cubes 2 sticks butter or margarine, cubed 6 squares unsweetened chocolate 2 Tbsp. light corn syrup 2 -16 oz. packages (about 8 cups) powdered sugar 1-1/2 cups chopped pecans 1 tsp. vanilla PLACE Velveeta, butter, chocolate and corn syru...