In a large mixing bowl, combine the flour, granulated sugar, and salt.
Add the cold, cubed butter and use a pastry cutter or your fingers to cut the butter into the flour mixture until it resembles coarse crumbs.
Add the egg and 2 tablespoons of cold water, mixing until the dough comes together. If the dough is too dry, add an additional tablespoon of cold water.
Form the dough into a ball, wrap it in plastic wrap, and refrigerate for at least 30 minutes.
In a medium saucepan, combine the granulated sugar, honey, heavy cream, and butter.
Cook over medium heat, stirring constantly, until the mixture comes to a boil.
Reduce the heat and simmer for about 5 minutes, or until the mixture thickens slightly.
Stir in the chopped walnuts and remove from heat. Allow the filling to cool slightly.
Preheat your oven to 350°F (175°C).
On a lightly floured surface, roll out two-thirds of the chilled dough into a circle large enough to fit a 9-inch tart pan with a removable bottom. Press the dough into the pan and trim any excess.
Pour the walnut filling into the pastry shell and spread it evenly.
Roll out the remaining dough into a circle and cut it into strips to create a lattice top, or simply cover the tart with the rolled-out dough, sealing the edges.
If you are covering the tart entirely, make a few small slits in the top to allow steam to escape.
Bake in the preheated oven for 25-30 minutes, or until the pastry is golden brown and the filling is bubbly.
Remove from the oven and allow the tart to cool in the pan on a wire rack.
Once the tart is completely cool, remove it from the tart pan and transfer it to a serving plate.
Enjoy your meal!