To make the shortcrust pastry, sift the flour, add the cold butter cut into cubes, and use your fingertips to rub them together until the mixture resembles breadcrumbs.
Add the sugar and mix again, then in go the egg yolk and water.
Knead to get a smooth dough.
Cover it with clingfilm, and chill it in the fridge for 10-15 minutes to the dough can rest.
Use a rolling pin to a roll it over, then arrange it over a pie/quiche pan.
Cut out the excess dough, and use a fork to prick the dough in several places.
Cover the pan with kitchen foil, then add baking beans or any dry pulses you have around.
Blind bake the crust for 15 minutes in the preheated oven at 200 degrees Celsius (390 Fahrenheit).
Remove the beans and the foil, and bake the crust for a further 5 minutes.
Add the roasted sweet potatoes to a large bowl and use a hand mixer to mix them well.
Add the eggs, white and brown sugar and spice and beat again until you get a smooth filling.
Pour the mixture over the baked crust, and bake at 180 degrees Celsius (350 Fahrenheit) for 30 minutes or until the filling is set and the pastry is golden.
Leave to cool completely, then beat the cream until it holds stiff peaks, and add it to a piping bag fitted with a star nozzle.
Decorate and serve cold from the fridge!