Preheat the oven to 180 C / Gas 4. Grease a 23cm round pie dish.
Lay the sliced peaches in the dish. Sprinkle with the demerara sugar and cornflour. Stir gently.
In a mixing bowl, combine the spelt flour, plain flour, caster sugar, baking powder and salt. Rub in the butter till the mixture resembles coarse breadcrumbs. Add the milk and beaten egg, and stir until just combined (do not overmix).
Using a tablespoon, drop spoonfuls of the cobbler topping over the peaches. I usually do several around the edges and then one in the centre.
Bake in the preheated oven for 35 to 40 minutes, or till the topping is golden and the peaches are soft.
Serve on its own or with Greek yoghurt, custard, creme fraiche, mascarpone or vanilla ice cream.