In a small bowl, combine flour, sugar, baking powder, milk and salt; stir until well blended. Spread evenly in a lightly greased 9-in. square baking dish. in a saucepan, combine raisins, brown sugar, water and butter. Bring to a boil. Stir in vanilla. Pour gently over flour mixture. Do not stir. Bake at 350° for 30 minutes. Serve warm with whipped cream.