To make the pastry, place the butter, flour and salt in bowl and rub together with your finger tips until a fine crumb consistency is achieved. Add a splash of water and work to form a dough (if it’s still too crumbly add a touch more water). Wrap the dough in clingfilm and leave to rest in the fridge for at least an hour and up to 3 days.
Remove the rested dough from the fridge and, as it is coming to room temperature, make the filling by combining all the ingredients in a bowl and, using your hands, mix together well.
Roll the pastry out to around a 30cm circle (ish! Thankfully galette’s can be any shape when rolled out really!) and transfer to a tray lined with parchment paper.
Spoon over the filling leave a 1cm gap all around the outside before folding over the sides to trap in the filling. Brush the edge all over with a beaten egg and sprinkle all demerera sugar.
Your oven needs to be fully saturated but with no flame presence – you’re looking for a floor temperature of around 240 degrees. Pop the tray into the oven before putting on the door. Cook for 35 minutes (but check every 10 to ensure it’s cooking well).
Transfer the gallette to a serving plate and serve with cream or ice cream.