Place 1 tablespoon of the butter in a 23cm round cake tin and place in oven to melt. Once the butter has melted remove the pan from the oven and stir in the brown sugar. Spread to coat the bottom of the pan evenly. Arrange the peach slices in the pan and set aside.
Separate the eggs. In a small bowl, beat the egg whites until stiff peaks form. Set aside.
Cream the remaining butter with the white sugar. Beat in the egg yolks, then the milk and the vanilla essence.
Stir the biscuit crumbs, baking powder and salt together. Beat the crumb mixture into the egg yolk mixture. Gently fold the beaten egg whites into the batter. Pour the batter into the prepared pan over the top of the peaches.
Bake for 40 minutes. Remove cake from oven and immediately invert the cake upside down onto a large plate. Because this cake is so moist, it should be stored in the refrigerator. Makes about 8 servings.