Add boiling water, salt, sugar and butter into the thermomix and set it to boil (veroma).
When the water boils, add in the flour. Beat at #4 until the batter cools down slightly (and won't cook the eggs)
Add the eggs one at a time into the thermomix at #5
Once you get the 'V', stop adding the eggs. If the mixture is too thick, add milk.
Beat until the mixture is shiny.
Place the mixture into a piping bag and plain #11 nozzle, and pipe about 1.5 cm rounds of choux pastry.
Place disc of croustillant on top of each choux ball.
Bake at 220C till puffed and golden brown all over. Lower the heat to 180C and cook for a further 30 minutes or so until perfectly dry.