Preheat oven to 425 degrees F. Line a baking sheet with parchment paper; set aside.

In a large saucepan over medium-high heat, combine the butter, water, and salt. Bring to a boil and working quickly and carefully, add in the flour and beat vigorously with a wooden spoon until mixture forms a ball, is mostly smooth and comes together. Remove from the heat and cool for 10 minutes.

Add in your eggs, one at a time, beating well with the wooden spoon or a mixer until just combined. The mixture may look curdled and separated for awhile, but by the fourth egg it should definitely have come together into a soft dough.

Using two spoons, drop heaping 1/4 cupfuls of dough 2" apart on the baking sheet. If you get two baking sheets out of the dough, only bake one at a time - you want to minimize going into the oven to check on these as each time you open the oven door, you risk the cream puffs collapsing.

Bake for 20-25 minutes or until cream puffs are golden brown and appear dry. Remove from the oven and cool on a wire rack. Let cool thoroughly, about 1 hour. Split the top 1/3 of the cream puff off with a serrated knife.

For the filling: In the bowl of a stand mixer, cream together the heavy cream, confectioners' sugar, and vanilla on high speed until stiff peaks form. Pipe the whipped cream in the cream puffs and top with the cream puff lid. Dust with additional confectioners' sugar, if desired. Cream puff shells can be made a day in advance. Filled cream puffs should be eaten same day.