To make the pastry, start by sifting the flour and confectioners' sugar into a large mixing bowl.
Then roughly chop the butter into cubes and toss them into the bowl with the dry ingredients. Using your fingertips, rub the butter into the flour until you have a mixture that feels like coarse sand. Try to work quickly here, so that it doesn’t become greasy, and keep rubbing until there are no large clumps of butter remaining.
Crack the eggs into the bowl and use your hands to bring the dough together, working it gently until it becomes smooth and pliable. Be careful not to overwork the dough, as this will make the pastry tough.
Roll the pastry into a ball, wrap in greaseproof paper, and put it in the fridge to chill for at least 30 minutes.
Grease a 10-inch (25-centimeter) wide pie dish. Divide the pastry into two chunks (one of roughly 1/3 and the other 2/3)
Lightly dust the kitchen work surface with flour and roll out the larger chunk of chilled dough to roughly 1/8-inch (1/2-centimeter) thick, before carefully draping it over the dish. Leave the rest of the dough to rest in the fridge.
Gently ease the draped dough into the nooks and crannies of its pan and leave a little overhang over the edges. Prick the bottom of the pastry all over with a fork, then cover with greaseproof paper and chill in the fridge for another 15 to 20 minutes. This will help stop the pastry from shrinking down when you bake it.
Preheat the oven to 350° F (180° C).
Weigh down the greaseproof paper with baking beans (or pie weights or uncooked rice) and blind bake in the oven for 15 to 20 minutes, until the edges of the pastry begin to brown slightly and the bottom cooks a little.
Meanwhile, slice the pears and set them to one side. Then roll out the rest of the pastry and use a cookie cutter to cut it into small leaf shapes.
Take the pastry out of the oven, discard the greaseproof paper, and spoon the chestnut purée into the pie. Spread evenly and top with the pears.
Arrange the pastry leaf shapes around the edge of the pie, so that they overlap with the crust.
Using a pastry brush, lightly glaze the pastry leaves with the egg, and sprinkle with the superfine sugar.
Set the pie in the oven and bake for a further 15 to 20 minutes, until golden on top.
Spoon away any excess juices from the pears and serve warm or at room temperature.