To make the craquelin, mix the flour, sugar and butter together in a bowl, using your fingertips rub the ingredients together until they resemble breadcrumbs.
Then press the breadcrumbs together until they form a dough. Place the dough between two sheets of greaseproof paper and roll out the dough until it's 2mm thick. Place the dough on a baking tray, still covered in the greaseproof paper and put it in the freezer.
After about 30 minutes, remove the craquelin from the freezer and cut out as many 2.5cm circles as you can fit on the whole sheet. Return the circles to the freezer.
Take the puff pastry and roll it out to around 5mm thickness, cut out a 23cm circle using a plate or a cake tin as a guide. Transfer the pastry circle to a baking tray, prick the base with a fork and transfer to the fridge.
Make the choux pastry according to the recipe, take the puff pastry out of the fridge and pipe a circle of choux pastry 1cm in from the edge of the puff pastry base. Then pipe another circle 2cm in from the first circle, so that you have two rings on the puff pastry base.
Preheat the oven to 180C (160C Fan) Gas 4, prepare two baking sheets and draw 2.5cm circles on the reverse of some baking parchment, use all of the choux pastry and pipe blobs (you will have more than you need, but choux can't really be made in quantities smaller than this and there is enough salted caramel and creme chantilly left over for you to fill the choux puffs).
Top each blob with a circle of the craqulin and bake the puff pastry base and the choux buns for 35 mins. Then turn the oven off and leave them to cool in the oven for a further 15 mins.
Remove from the oven and allow to cool completely.
While the choux is cooking, make the creme chantilly, add the cream to a large bowl, add the vanilla extract and sift in the icing sugar. Whip the cream until it forms stiff peaks. Place a third of the cream in a piping bag fitted with a St Honore piping tip. Place the rest of the cream in a piping bag fitted with a 1cm straight piping nozzle. Return to the fridge.
Take the salted caramel, if it's too thick or too cold, warm it in the microwave on a low heat for 30 seconds, you want it to be piping consistency, but not too runny. Place the caramel in a piping bag fitted with a 1cm straight piping nozzle.
Take the choux puffs and with a sharp knife, pierce a hole in the bottom of each puff, making sure it's big enough for the piping nozzle to fit in.
Fill each choux puff with some salted caramel and then fill completely with the chantilly cream in the piping bag with the straight nozzle.
Take the remaining salted caramel and pipe it in the centre of the pastry base and in between two two bands of choux pastry.
Before you make the caramel, make sure you have everything you need to hand. Place the puff pastry base on a wire rack with some greaseproof paper underneath, line up the choux puffs which you want to use on the gateau.
Next make the caramel, this will be the glue that keeps the whole gateau together. To make caramel, put half the sugar in a heavy based pan and melt it over a gentle heat. Add the rest of the sugar and melt until it becomes an amber caramel colour.
Dip the top of the choux puff in the caramel, you can place it in a silicone semi-sphere mould to set the caramel evenly. When cool, dip the bottom of the choux puff in the caramel and stick this to the ring of choux pastry, keep going until you have a complete ring of choux buns.
Then take the creme chantilly with the St Honore nozzle and pipe stripes in the centre of the St Honore.