Preheat the oven to 150 C / Gas 2 and line a baking tray with baking parchment.
Sift the flour into a mixing bowl. Add the butter to the flour and rub together until the mixture resembles fine breadcrumbs. Gradually add just enough water to bring the mixture together into a firm dough. Knead lightly then wrap in cling film and chill in the fridge for 1 hour.
Cut the sausages in half and squeeze out the meat from the skins into a bowl. Add the spring onions and season with salt and pepper. Mix together with your hands.
Remove the pastry from the fridge. Sprinkle some flour onto a work surface and roll pastry out to desired shape remembering to leave some for the top. After you have rolled out the bottom, cut strips of the remaining pastry for the lattice top.
Carefully place your sausage mixture on top of your bottom piece of pastry and spread evenly. Place the strips of pastry on top of the sausage mixture in a nice fashion and roll the edges of the pastry to make a nice crust. Brush with beaten egg.
Bake in the preheated oven until the sausage is no longer pink and the pastry is golden brown, about 25 to 35 minutes. Remove from the oven and serve warm or allow to cool on a cooling rack before serving.