To make the shortcrust pastry combine the flour, cubed butter and sugar in a food processor and blitz for about a minute. Slowly pour in the water as the blades are rotating, and stop the processor as soon as the mixture reaches a crumbly texture.
Set aside 200 g of crumbles, then start the processor again and let it work until the dough gathers into a ball.
Press the dough all over the bottom of a tart pan, prick bottom and sides with a fork and bake in the preheated oven at 180°C (350°F) for 15 minutes.
In the meantime, prepare the curd. Combine the sugar, lemon juice and zest, butter and grated ginger and set on a double boiler. Stir from time to time until both the butter and sugar dissolve.
Crack the eggs in a bowl and give a whisk by hand. When the lemon mixture looks homogeneous, pour in a couple of tablespoons of the hot mixture into the eggs, whisking constantly with the other hand to prevent the eggs from scrambling.
Start whisking the lemon mixture, which should be still cooking on the double boiler, and slowly pour the egg mixture into it as you whisk. Keep whisking for a couple of minutes after you have added all the eggs. Keep cooking until the mixture thickens enough to coat a spoon, 5 minutes. Remove from the double boiler.
After the shortcrust shell has pre-baked, take it out of the oven and pour the lemon curd all over. Top with the crumbles you had set aside making sure to cover all the surface. Return the pie to the oven and bake for another 25 min.