For the pastry, place the flour, butter, egg, sugar and milk into a food processor and pulse briefly to bring the ingredients together as a dough. Remove and place into a bowl and mix well with your hands, then cover and place into the fridge to chill for 20 minutes.
Dust a clean flat surface with a mixture of flour and icing sugar and roll out the pastry. Place the pastry into a 20cm/8in tart case and return to the fridge to chill for two hours.
Preheat the oven to 200C/400F/Gas 6.
Place the tart case into the oven, covered with a sheet of baking paper weighed down with baking beans and bake blind for 25 minutes, or until golden, but not browned. Remove the baking paper and beans, brush with the egg wash and return to the oven for five more minutes, then remove and leave to cool.
For the filling, place the pumpkin and butternut squash onto a baking sheet, sprinkle with the sugar and place into the oven to roast for 40 minutes, then remove and allow to cool slightly.
Place the pumpkin and butternut squash into a food processor and blend until smooth.
Reduce the oven temperature to 180C/355F/Gas 4.
Meanwhile, place the cream, honey and spices into a saucepan over a medium heat and bring to simmering point.
Place the beaten eggs into a clean bowl and pour over the cream mixture, whisking constantly.
Add the pumpkin mixture to the pan, stir well to combine, then pour into the tart case.
Transfer the tart to the oven and bake for 35 minutes, or until the filling has set. Remove and leave to cool.
For the custard, whisk the eggs, sugar and vanilla together in a clean bowl.
Place the milk into a clean saucepan and heat up to near boiling point, then remove from the heat and pour over the egg mix, whisking constantly.
Place the custard mixture back into the milk pan and simmer over a low heat, stirring regularly, until the custard thickens enough to coat the back of a spoon.
To serve, cut a generous slice of the butternut squash and pumpkin pie, place onto a plate and serve with the homemade custard drizzled over the top.