Rhubarb, ginger and custard galette

Method

1. In a bowl, stir together the flour, ginger and a pinch of salt. Rub in the butter until the mixture resembles breadcrumbs. Add roughly half the beaten egg and 2-3 tbsp ice-cold water to bring the mixture together into a dough. Knead briefly then flatten into a disc, cover and chill for at least 30 minutes.
2. Heat the oven to 180°C fan/gas 6 with a large, flat baking tray inside to heat up. On a lightly floured worksurface, roll the pastry out to a circle roughly 35cm wide and transfer to a sheet of baking paper. Use a plate or a cake tin to lightly indent a 25cm circle in the centre to use as a guide. Sprinkle the custard powder over this central circle then scatter over the stem ginger.
3. Arrange the rhubarb on top of the custard powder in diagonal lines or a geometric pattern of your choice, ensuring the ends sit closely together. Drizzle the ginger syrup over the rhubarb, then fold the pastry border up over the fruit. Brush the pastry with the remaining egg, then sprinkle the demerara sugar all over.
4. Carefully slide the galette (and the paper it sits on) onto the preheated baking tray and bake for 20-25 minutes until golden. Brush with a little more ginger syrup if you like and serve warm with custard.