Pie crust:

1. In a bowl, mix together the dry ingredients, flour, sugar and salt then add the cold butter pieces.
2. With your hands, crush the butter and mix it with the other ingredients until you have a sandy mixture with a few small pieces of butter still visible.
3. Then add the cold water and gather the dough until you get a ball of dough which is not very homogeneous.
4. Cover with plastic wrap and place in the fridge for at least 30 minutes.
5. Roll out the dough between 2 sheets of parchment paper to a thickness of 3 to 4 mm.
6. Line a 9 inch / 22 cm pie pan greased with butter with the dough.
7. Prick the bottom of the pie with a fork and place in the freezer while preparing the filling.

Walnut filling:

1. Preheat oven to 350°F / 180°C.
2. In a large bowl, place the softened butter with the brown sugar and mix with an electric mixer for 2 minutes until creamy.
3. Add the eggs and vanilla and mix again for 1 minute to incorporate them.
4. Add the remaining ingredients, corn syrup (or honey and maple syrup mixture), flour, salt and crushed walnuts.
5. Mix with a soft spatula or wooden spoon until the mixture is smooth.
6. Pour the mixture into the pie pan containing the pie crust.
7. Bake for 30 to 35 minutes until the dough is golden brown and the filling is firm.
8. Let cool completely at room temperature before removing from the pan and serving.