1. Male the pastry wreath: Preheat oven to 425 degrees. Trace a 9-inch circle onto a sheet of parchment. Flip parchment, making sure pencil mark is still visible, and place on a baking sheet.

2. In a medium saucepan over medium-high heat, combine butter, sugar, salt, and 1 cup water. Bring to a boil and immediately remove from heat. Using a wooden spoon, quickly stir in the flour until combined.

3. Return pan to medium-high heat and cook, stirring vigorously, until mixture pulls away from the sides and a film forms on the bottom of the pan, about 3 minutes.

4. Remove from heat and transfer contents to a bowl to cool slightly, about 3 minutes. Add eggs, one at a time, stirring vigorously after each addition, and waiting until each is entirely incorporated before adding the next egg. Use immediately.

5. Transfer pate a choux dough to a pastry bag fitted with a 1/2-inch plain round tip. Pipe a tiny dot under each corner of parchment, pressing to adhere parchment to baking sheet. Then pipe dough, tracing outline, into sixteen 1 3/4-inch mounds, holding pastry bag upright and keeping pressure consistent.

6. Whisk remaining egg with pinch salt. Brush egg over top of pastry wreath.

7. Bake until pastry just starts to puff, about 10 minutes. Reduce oven temperature to 375 degrees. Bake until pastry is fully puffed and golden brown, about 30 minutes.

8. Turn oven off, remove wreath, and pierce top and sides about 8 times using the tip of a sharp knife to release steam. Return to oven, and prop door open with a wooden spoon. Let stand for 1 hour to dry.

9. Transfer pastry wreath on parchment to a wire rack. Let cool completely.

10. Fill and decorate the pastry wreath: Whisk heavy cream, confectioners' sugar, and vanilla until soft peaks form. Separate pastry wreath into top and bottom halves using a serrated knife.

11. Spread about 1 1/2 cups pastry cream over bottom ring. Pipe whipped cream in a swirl using 1/2-inch closed star tip. Reposition top pieces of pastry wreath over filling. Dust with confectioners' sugar.