Heat oven to 200C/180C fan/gas 6.
Cut the squash into several large pieces,
remove any seeds, then toss with the oil
in a roasting tin. Roast for about 35 mins
or until golden and soft.
When cold, peel the skin away, then
put the flesh into a processor with the
sugar, mascarpone and spices. Whizz
until smooth, then add the eggs, maple
syrup, vanilla and ¼ tsp salt. Whizz again.
Cut one-third of the pastry from one
block and squash it into the other block.
Shape the larger block into a smooth
round then, on a floured surface, roll out
to line a 23cm fluted tart tin. Line the tin,
leaving some overhang, then lift onto a
baking sheet. Pour in the filling, then
carefully slide the pie into the oven and
bake for 20 mins.
Meanwhile, roll the remaining pastry
to a rectangle about 16 x 30cm, then cut
into 8 long strips about 2cm wide. Weave
the strips under and over each other on
a floured, rimless baking sheet to make a
lattice large enough to cover the top of
the pie. Put in the fridge to chill.
After 20 mins, the filling will be starting
to set. Take pie out of the oven, brush pastry
rim with milk, then slide the chilled lattice
off its sheet and onto the pie. Press the
edges down a little to seal, then scatter
over the pecans and return to the oven.
Bake for 15-20 mins more or until the
lattice is golden and the filling has risen
with just a faint wobble in the middle.
Cool completely, then trim the edges and
dust with icing sugar. Drizzle with maple
syrup and serve with whipped cream.