Place ¼ c. butter in an 8 x 8 baking dish. Preheat oven to 350 degrees and place baking dish with butter in oven until butter is melted. Remove pan from oven. Add brown sugar evenly around pan mixing with butter. Arrange peach slice in the brown sugar butter mixture and set aside.
In a medium bowl combine flour, baking powder and salt, set aside. In a large mixing bowl beat the ½ c. butter with an electric mixer on high speed for 30 seconds. Add sugar and mix well. Add egg and vanilla, mix until combined. Add flour mixture to the beaten butter mixture alternating with the milk until combined but not over mixing. Spread batter evenly over peaches and bake for 45-50 minutes or until a knife comes out clean.
While cake is cooling make the brown sugar whipped cream by whipping cream, sugar and vanilla until soft peaks form.
When cake is cool, invert onto a serving dish and top with whipped cream!