Cut the pumpkins on top (leave an opening of around 4 inches) and scrape out the flesh and seeds.
Place pumpkins in boiling water for 5 minutes, then remove, drain and cool.
Preheat oven to 300 F (150 C).
In a saucepan heat the heavy cream with pinch of salt. Remove from the heat, once it starts bubbling.
Whisk together the sweetener and egg yolks in a bowl.
Slowly add 1/4 of the hot cream, while whisking constantly.
Return the cream and egg yolk mixture to the pan. Cook on low-medium heat for 2 minutes, stirring constantly.
Add the vanilla, pumpkin puree and pumpkin pie spice. Stir to combine.
Pour the mixture into the pumpkins.
Place in a baking dish and add hot water, to cover about 1 inch of the bottom of the pumpkins.
Bake for 1 hour and 20-30 minutes. Cool completely. Refrigerate for up to 3 days.
When ready to serve, sprinkle some brown sugar (low carb sweetened) on top of the custard and brown with a pastry torch. Serve.