In a small sauce pan add balsamic vinegar and heat over medium until it begins to boil. Allow to reduce for 1 minute, stirring often. Set aside.
In a medium sauce pan stir together raspberries, sugar and water. Cook over medium heat until raspberries are mashed down and mixture is bubbling. Continue to cook until thick and syrupy, stirring often, approximately 10 minutes. Strain using a fine mesh sieve, pressing solids against the sides to expel as much juice as possible. Discard solids and stir reduced balsamic vinegar and 1/2tsp vanilla into raspberry juice. Cool until chilled.
Whip cream and 1tsp vanilla until stiff peaks form. Fold sweetened condensed milk into whipped cream. Pour half into a 9"x5" loaf pan. Drizzle half the raspberry sauce over the cream mixture. Pour remaining cream mixture over to cover completely. Top with remaining raspberry sauce and swirl using a bread knife. Cover and freeze for at least 8 hours.