Mix powdered gelatin with cold water in a small bowl and allow the mixture to bloom for 5-10 minutes.

In a large heatproof bowl, whisk together sugar, cornstarch, eggs, egg yolks and pumpkin pie spice.

In a large saucepan, combine cream and milk. Heat the mixture over medium heat until it comes to a simmer.

Remove the cream and milk from the heat, and whisking continuously, slowly pour the hot cream mixture into the egg and sugar mixture until the eggs are tempered.

Pour the mixture back into the same large saucepan and place over medium heat, whisking constantly.

Increase heat to medium high and whisk until mixture becomes bubbly and thick, approximately 1-2 minutes. Remove from the heat.

Whisk the bloomed gelatin into the hot pastry cream until it is completely melted down.

Place a fine sieve over a large heatproof bowl. Pour the pastry cream into the sieve to catch any bits of egg that may have coagulated.

Remove the strainer from over the bowl.

Whisk vanilla extract, pumpkin purée and butter into the pastry cream until well combined and butter is melted.

Place a piece of plastic wrap directly onto the surface of the pastry cream and refrigerate for at least one hour.

Use pastry cream before it becomes too firm to scoop into small glasses or into a tart or pie shell. Chill in refrigerator.