To make the pastry shells, preheat oven to 400°F (200°C). Line 2 baking sheets with parchment paper, or silicone mat.
In a medium saucepan, combine water, butter and salt. Bring the mixture to a boil over medium high heat.
Once the butter is melted and mixture is boiling, add the flour all at once, reduce the heat to medium. Using a wooden spoon, continuously stir the mixture. The dough will start to form into a ball. Keep mixing for another 3-4 minutes until light crust forms on the bottom of the pan.
Transfer the dough into a mixing bowl with paddle attachment and mix it for a few minutes on low speed until the mixture is at room temperature. (Alternatively, you can use a wooden spoon. Mixer is not required here!) Add the eggs one at a time, beating well after each addition. This will help to get egg absorbed into the dough quicker. The dough should not be too runny, yet not too thick.
Transfer the batter into a pastry bag and pipe into 1.5-inch rounds couple inches apart. Level peaked tops with wet fingertip, if needed.
Bake for 23-25 minutes, rotating the sheets top to bottom and back to front half way. The pastry shells should be golden brown, crispy and puffed up.
Transfer the shells onto a cooling rack to cool completely. (If the pastry shells fall flat when you remove from oven, it means they are under-baked. Simply put it back into the oven and bake for another 3-5 minutes, or until they puff up again.)
To make the filling, in a mixing bowl with whisk attachment whip the heavy cream until soft peaks form.
In another mixing bowl, beat cream cheese and pumpkin puree until smooth. Add powdered sugar and pumpkin pie spice and continue to beat until nice and fluffy.
Fold in the whipped cream until well combined.
When ready to serve, cut the cream puffs horizontally, fill the puffs with filling and replace the tops. If desired, dust with powdered sugar for decoration and serve.
Make-ahead Tip: Pastry shells can be made a day or two in advance and stored at room temperature, covered. The filling also can be made ahead, but needs to be refrigerated, covered. It’s best to fill the cream puffs the day you plan on serving them.