Prepare the Puff Pastry

1. Preheat the Oven: Preheat your oven to 400°F (200°C).
2. Prepare Puff Pastry: Roll out the puff pastry on a lightly floured surface. Cut a 9-inch circle from the pastry and place it on a baking sheet lined with parchment paper.
3. Prick the Dough: Use a fork to prick the center of the puff pastry to prevent it from puffing up too much.
4. Bake: Bake for 15-20 minutes or until golden brown. Let it cool on a wire rack.

Make the Cream Puffs

1. Prepare the Dough: In a medium saucepan, combine water, butter, salt, and sugar. Heat over medium until the butter melts. Once it starts to simmer, remove from heat and stir in flour.
2. Add the Eggs: Once the dough cools slightly, add eggs one at a time, mixing well after each addition until the dough is smooth.
3. Pipe the Puffs: Transfer the dough into a piping bag and pipe small mounds onto a baking sheet lined with parchment paper.
4. Bake the Cream Puffs: Bake at 400°F (200°C) for 20-25 minutes or until golden and puffed up. Let cool on a wire rack.

Prepare the Pastry Cream

1. Heat the Milk: In a medium saucepan, heat the milk over medium heat until it just begins to steam.
2. Whisk the Yolks: In a bowl, whisk together the egg yolks and sugar until smooth. Add the cornstarch and whisk until combined.
3. Temper the Eggs: Slowly pour the hot milk into the egg mixture, whisking constantly. Return the mixture to the saucepan and cook over medium heat, whisking constantly, until it thickens (about 3-5 minutes).
4. Add Butter and Vanilla: Once thickened, remove from heat and stir in the butter and vanilla extract.
5. Cool the Cream: Pour the pastry cream into a bowl and cover with plastic wrap. Allow it to cool completely in the fridge.

Make the Caramel

1. Prepare the Caramel: In a small saucepan, combine sugar and water. Stir over medium heat until the sugar dissolves.
2. Caramelize: Increase the heat to medium-high and cook without stirring until the mixture turns a deep amber color (about 5-7 minutes).
3. Add Butter and Cream: Carefully add the butter and heavy cream, stirring until smooth. Allow to cool to room temperature.

Assemble the St. Honoré Cake

1. Whip the Cream: Whip the heavy cream until soft peaks form.
2. Fill the Cream Puffs: Once the cream puffs are cooled, use a piping bag to fill each puff with the cooled pastry cream.
3. Assemble the Layers: Place the puff pastry circle as the base. Arrange the filled cream puffs around the edge, creating a circular shape.
4. Add the Caramel: Carefully drizzle the cooled caramel over the cream puffs.
5. Top with Whipped Cream: Pipe whipped cream into the center of the cake.
6. Final Touch: Lightly dust the cake with powdered sugar for a finishing touch.