In a small saucepan, melt the butter with the brown sugar over medium heat. Stir continuously, until the brown sugar dissolves. Remove from heat, whisk in vanilla extract and set aside to cool. Beat the cream cheese and confectioners? sugar for 1 minute. Slowly beat in the cooled butter mixture and beat again for another minute. Stir in the chocolate chips. Pour into a serving bowl and refrigerate. Garnish with additional chips, if you choose. Serve with wafers or graham crackers. After refrigerating the dip, it will be pretty solid. Remove it from the refrigerator about 15-30 minutes before you plan on serving it, so it has time to soften up.