Preheat the oven to 180˚C (160˚C for fan assisted ovens)/ Gas Mark 4. Mix together the melted butter and the light brown sugar then spread in the base of the lined tin. Arrange the pear slices in a circle in the base of the tin with the point of each slice meeting in the centre.
Mix the eggs, oil, water and cake mix gently together and whisk (by hand or electric mixer) for 2-3 minutes until smooth and creamy.
Pour the cake mixture over the pears and gently level the surface.
Bake in the centre of the oven for 45-55 minutes, or until risen, firm to the touch and a skewer inserted into the centre of the cake comes out clean. Leave in the tin for 10-15 minutes.
Meanwhile, make the chocolate sauce. Gently heat the chocolate icing and milk in a small pan, stirring all the time, until melted and smooth. Cool for 5-10 minutes to allow the sauce to thicken slightly, stirring occasionally.
To serve, invert the cake onto a serving plate or board. Cut into slices and serve with the warm chocolate sauce and cream (optional).