Bring the water, sugar, salt, milk, and butter to a boil.
Pour into a mixing bowl with all of the flour.
Paddle until cooled, but still warm. Add in eggs in 3 additions.
Pipe rounds onto a tray lined with a Silpat macaron template.
Optionally, add the croustillant round on top of each choux.
Bake at 350˚F (177˚C) for 20 minutes, then 325˚F (163˚C) for 20 more minutes.