Roast the sweet potatoes

1. Preheat the oven to 180°C/350°F. Line a baking tray with parchment paper.
2. Wash and dry approximately 3 large orange-fleshed sweet potatoes. Prick each potato several times with a fork and place them on the prepared tray.
3. Roast for 45 to 65 minutes, depending on their size. They are ready when a knife slides easily into the thickest part.
4. Leave the potatoes until cool enough to handle. Split them open and scoop the flesh away from the skins.
5. Pass the flesh through a potato ricer or fine-mesh sieve to remove any coarse fibres. Weigh exactly 600 g of purée and allow it to cool.

Prepare the pastry

6. Place the flour and salt in a mixing bowl. Add the cubes of cold butter.
7. Rub the butter into the flour with your fingertips until the mixture resembles coarse breadcrumbs. Work quickly so the butter remains cold.
8. Add the ice-cold water gradually and mix gently with a fork or wooden spoon. Stop mixing as soon as the dough holds together when pressed. Add up to 1 extra teaspoon of water only if necessary.
9. Shape the dough into a disc without kneading it. Cover and refrigerate for 20 to 30 minutes.
10. Roll the chilled dough into a circle on a lightly floured surface. Use it to line a 20 cm/8-inch pie or tart pan, pressing it gently against the base and sides.
11. Trim the edges and refrigerate the lined pan while making the filling. Use the pastry trimmings to cut out decorative leaves, if desired, and keep them chilled.

Make the maple filling

12. Place the cooled sweet potato purée in a large bowl. Add the brown sugar, maple syrup and pumpkin pie spice, then whisk until evenly combined.
13. Beat the eggs lightly in a separate bowl before adding them to the purée. Mix gently to avoid incorporating too much air.
14. Slowly pour in the cooled melted butter and whisk just until the filling is smooth and uniform.

Assemble and bake

15. Place a heavy metal baking tray in the oven and preheat it to 180°C/350°F. The hot tray will help the bottom crust bake more evenly.
16. Pour the filling into the chilled pastry shell and smooth the surface. Arrange the chilled pastry leaves on top without completely covering the filling.
17. Set the pie pan on the preheated baking tray. Bake for 40 to 50 minutes. If the pastry edges brown too quickly, shield only the edges loosely with foil.
18. Check the pie near the end of the baking time. The edges should be set, while the centre should still have a small, gentle wobble when the pan is moved. It should not appear liquid.
19. Remove the pie from the oven and place it on a wire rack. Let it cool completely for at least 3 hours before cutting.
20. For the neatest slices, refrigerate the cooled pie for 1 to 2 hours. Serve chilled or allow each slice to stand at room temperature for about 15 minutes before serving.