In small heavy saucepan cook and stir condensed milk, chocolate, corn syrup and 1/4 cup of the milk over low heat until chocolate melts. Gradually stir in enough of the remaining 1/4 cup milk until dip is of desired consistency.
Stir in vanilla. Add nuts (if desired), stirring until combined. Serve warm with Keebler (R) Town House (R) Flipsides (R) Original Crackers.
Make ahead: Prepare dip as directed above. Cover and refrigerate for up to 1 week. Before serving, in small heavy saucepan cook and stir dip over low heat until heated through. Serve as above.
PER SERVING (2 tablespoons): 110 calories, 6g fat, 25mg sodium, 13g carbs, 2g fiber, 10g sugar, 3g protein