Preheat the oven to 180ºC.
Grease a square tin (20 cm in diameter) with margarine.
Place the custard powder and brown sugar in a saucepan and mix. Add the milk and heat until the mixture comes to the boil and thickens. Stir continuously. Add the butter and egg. Stir well and leave to cool to room temperature.
Cream the butter or margarine and the caster sugar until light and creamy. Add the eggs one by one and beat well. Then add the self-raising flour and milk and mix well.
Spoon half the batter into the prepared cake tin and spread evenly. Spread the custard mixture on top and arrange the peach slices on top of the custard mixture. Spoon the remaining batter on top.
Bake for 50 minutes at 180ºC, reduce the temperature to 150ºC and bake for a further 30 minutes. Cool to room temperature in the tin and then turn the cake out onto a wire rack. Dust with a little icing sugar before serving.
Recipe reprinted with permission of You