Combine brown sugar, flour and butter in a mixing bowl
Rub the butter into the flour and sugar using your fingertips
Place between two pieces of parchment paper and use a rolling pin to roll it out to 4mm in thickness
Freeze
Cut into 4cm or 1 1/2" inch round discs with a cookie cutter and reserve in the freezer until ready for use
Choux Pastry
Preheat the oven to 230°C
Line a baking sheet with parchment paper
Heat milk, water, butter, salt and sugar in a medium saucepan over medium low heat
When it starts to boil remove from heat and add the flour in one go, mixing vigorously until smooth
Return to heat and flatten the dough to the bottom of the pan, listening for crackling of the dough without mixing
Give the pan a shake and when you notice a thin film on the bottom of the pan the dough is sufficiently dry
Remove from heat
Using a wooden spoon/spatula beat the dough to let steam evaporate and then cool for 10 minutes
Slowly add the beaten egg and stir until the dough is smooth, but still holds structure (the batter will form a 'V' or a 'beak' on the spoon/spatula when lifted)
Pipe 5cm /2 inch round mounds onto the lined baking tray
Top with a disc of frozen craquelin
Turn down the oven temperature to 160°C and bake for 25 minutes, or until golden brown
Remove from oven and poke a hole in the bottom of each puff to release steam
Cool on a wire rack
Creme Patissiere
Heat milk until just boiling in a small saucepan
Meanwhile, in a medium sized mixing bowl combine egg yolks and sugar, whisking until doubled in volume
Add the cornflour and mix until combined
Pour the hot milk into the egg mixture and whisk until smooth
Return the mixture to heat and whisk constantly until thick
Remove from heat and add butter
Pour into a bowl and cover with plastic wrap, ensuring it touches the surface of the pastry cream
Cool in fridge until use
Diplomat cream
Whisk the cream until medium-stiff peaks are reached
Add the cooled creme patisserie and whisk until stiff peaks are reached
Transfer to a piping bag with small round tip
Reserve in the fridge until use
Assembly
Poke a hole at the bottom of each choux puff
Fill the choux with the creme diplomat
Place in the fridge as you prepare the caramel
Caramel
Combine the sugar and water in a small saucepan over medium heat
Heat the sugar, swirling the pan occasionally to ensure even heating
Continue to heat the sugar until it turns a golden brown
Remove from the heat and working quickly dip the tops of your choux pastries into the caramel
Place the dipped choux caramel side up on a baking tray lined with parchment paper