In a small saucepan, heat the butter and water till the butter dissolves on medium heat.
Remove from the heat, add in the flour and use a wooden spoon to mix till a dough comes together in a ball.
Allow to cool for one minute.
Place the dough in a stand mixer with a paddle attachment.
Turn the mixer on medium low and add the eggs one at a time. Allow each egg to incorporate before adding the next one.
After the addition of the last egg, you should see a shiny dough formed.
Place the dough in a pastry bag with a medium star tip ( I used Ateco #867).
Preheat oven to 400 degrees.
On a sheet of parchment paper, draw a 10″ circle in pencil. Flip the sheet over and place on a baking sheet.
Pipe rosettes of dough around the perimeter of the circle that you drew, in a continuous pattern till you have a ring of piped dough around the entire perimeter. If desired, pipe a star in front of the rosettes.
Brush the pastry with egg wash and bake 10 minutes. Lower the oven temperature to 375 then bake for about 30 min longer till the pastry is a medium golden brown and puffed. Make sure the pastry is a medium to dark golden or it will be raw on the inside.
Remove from the oven and cool completely.
The pastry cream will need to chill, making this up a day ahead and allow to sit in the refrigerator is ideal.
In a saucepan, bring the milk and orange peels up to a steep.
In a separate bowl, whisk the sugar, cornstarch, and egg yolks together till combined. Temper the hot milk into the yolks whisking constantly. Pour the mixture back into the saucepan and bring to a boil whisking constantly.
Boil the mixture for 1-2 minutes till thickened. It will be thickened significantly.
Remove from the heat and stir in the extract and butter and mix till combined.
Immediately pour into a bowl and cover with saran wrap making sure the saran wrap sits on top of the custard so it does not develop a film on top. Place in the refrigerator to cool at least 4 hours or overnight.
Place the Paris-Brest on a serving platter. Pipe dollops of pastry cream with a plain tip or star tip around the perimeter of the Paris-Brest. Pipe the same with the fresh whipped cream.
Garnish with fresh orange supreme slices on top of the whipped cream. Dust with powdered sugar.
Serve immediately or refrigerate lightly covered until ready to serve.