Step 1: Make the Choux Pastry

1. Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
2. In a medium saucepan, combine the butter, water, and salt. Bring to a boil over medium heat.
3. Once boiling, reduce the heat to low and stir in the flour. Mix vigorously with a wooden spoon until the dough forms a ball and pulls away from the sides of the pan.
4. Remove the pan from heat and let the dough cool for 5 minutes.
5. Add the eggs one at a time, mixing thoroughly after each addition. The dough should be smooth and shiny.
6. Using a piping bag or a spoon, drop tablespoon-sized mounds of dough onto the prepared baking sheet, leaving about 2 inches between each puff.
7. Bake for 20-25 minutes or until golden brown. Avoid opening the oven during baking to prevent deflating.
8. Once baked, cool completely on a wire rack.

Step 2: Prepare the Cream Filling

1. In a mixing bowl, whip the heavy cream, powdered sugar, and vanilla extract until stiff peaks form.
2. Transfer the whipped cream into a piping bag fitted with a small tip.

Step 3: Fill the Cream Puffs

1. Slice each cooled puff in half horizontally or make a small hole in the bottom.
2. Pipe the whipped cream filling generously into each puff.
3. Replace the top if halved or seal the hole carefully.

Step 4: Freeze the Cream Puffs

1. Arrange the filled cream puffs in a single layer on a baking sheet and freeze for 2-3 hours until firm.
2. Transfer the frozen cream puffs into an airtight container or freezer-safe bag for storage.