For the Cream Puff Shells:

1. Preheat the Oven:
   Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper or a silicone baking mat.

2. Make the Dough:
   In a medium saucepan, combine the butter and water. Bring it to a boil over medium-high heat. Once boiling, remove from the heat and stir in the flour and salt all at once. Return to the heat and stir constantly for about 1-2 minutes, until the mixture pulls away from the sides of the pan and forms a smooth dough.

3. Add the Eggs:
   Remove the saucepan from the heat and allow the dough to cool for a minute. Add the eggs one at a time, beating well after each addition until the dough is smooth and glossy.

4. Pipe the Dough:
   Using a spoon or piping bag, drop or pipe small mounds of dough (about 1 to 1 1/2 inches in diameter) onto the prepared baking sheet. Leave about 2 inches between each puff to allow for spreading.

5. Bake the Shells:
   Bake the cream puffs in the preheated oven for 20-25 minutes, or until they are golden brown and puffed up. Do not open the oven during the first 15 minutes of baking, as this can cause the puffs to collapse.

6. Cool:
   Remove the cream puffs from the oven and allow them to cool completely on a wire rack. Once cool, use a small knife or skewer to make a small hole in the side of each puff for filling.

For the Cream Filling:

1. Whip the Cream:
   In a mixing bowl, beat the heavy cream with the powdered sugar and vanilla extract until soft peaks form. Be careful not to overbeat the cream.

2. Fill the Puffs:
   Once the cream puffs are cool, use a piping bag fitted with a small round tip or a spoon to fill the puffs with the whipped cream.

For the Glaze (optional):

1. Make the Glaze:
   In a small bowl, combine the powdered sugar and 1 tablespoon of milk or water. Stir until smooth. If you want a thinner glaze, add a little more milk or water until you reach your desired consistency.

2. Drizzle the Glaze:
   Drizzle the glaze over the top of the filled cream puffs for a sweet finishing touch.