Preheat oven to 350°F (175°C) and grease a 9-inch baking dish or 8 ramekins.

Whisk pumpkin puree, eggs, cream, milk, sugars, vanilla, and spices in a large bowl until smooth.

Mix cornstarch with 2 tablespoons of the pumpkin mixture to create a slurry, then stir into the main mixture.

Whisk the mixture for 2 minutes until combined and slightly frothy.

Pour into the prepared dish and tap to release air bubbles.

Place the dish in a roasting pan and add hot water until it reaches halfway up the sides of the baking dish.

Bake for 45-55 minutes for a large dish or 25-30 minutes for ramekins until the edges are set.

Cool in the water bath for 15 minutes, then remove and cool completely on a wire rack.

Refrigerate for at least 4 hours to set fully before serving chilled with whipped cream and a dusting of cinnamon.