Place flour, sugar and salt in the food processor and mix to combine.
Cut up butter into tablespoon segments and add to flour mixture.
Pulse until butter is combined and all ingredients become a cornmeal consistency.
Slowly add ice water a tablespoon at a time and pulse each time.
Continue to pulse until a dough starts to form, then tip onto a floured surface and mold into a mound.
Wrap pastry in plastic wrap and store in a fridge for 30 minutes.
Remove pastry from the fridge and roll out into a circle at least 3 inches wider than your pie dish.
Rub butter on all sides of the inside of your pie dish.
Carefully place pastry into pie dish making sure to carefully push pastry into base on all sides. Leave excess pastry to hang over the pie dish.
Place pie dish on a baking sheet in the fridge again for another 30 minutes.
After 30 minutes remove pie dish and adjust pastry if necessary then roll rolling pin over the top of the pie dish to remove the excess pastry.
Mould excess pastry into a mound and freeze for use at another time.
With a fork prick pastry base a few times.
Cut a circle of parchment paper to cover the base of the pastry, then place pie weights on top and place in a preheated oven at 420 and bake until the pastry edges become golden. Approx. 20 mins.
While pastry is baking pour pumpkin puree, honey, salt, cinnamon, allspice and nutmeg into a blender and blend on high until the pumpkin becomes smooth and has a glossy sheen.
Transfer pumpkin puree mixture into a saucepan and place saucepan on high heat and stir until the pumpkin mixture is heated through and you can smell the combined ingredients.
Remove from the heat and add vanilla and mix thoroughly.
Whisk oat milk, cream and eggs, then spoon in 2-3 tbsp of the pumpkin mixture into the egg mixture to warm it and stop the eggs from cooking and solidifying. Test with finger and add more puree mixture if needed.
Pour the warmed egg mixture into the pumpkin mixture and mix thoroughly.
Once pastry is blind baked remove the pie weights and parchment.
Tip pie filling into pie case then place pie dish on a cooking sheet and place into a preheated oven at 375.
Cook until pie filling becomes mostly solid in the outer areas but still quivers in the middle. Approx. 50 mins
Allow to cool before serving with whipped cream.