This is a truly spectacular celebratory dessert, often used in place of a cake at french weddings. Our version is a tower of hazelnut cream filled choux buns coated and stuck with crunchy golden caramel.
Preheat the oven to 200°C.
Add 500ml of water to a pan with the butter and a pinch of salt and heat to a boil. Remove the pan from the heat and whisk or beat in the plain flour until the mixture is coming away from the sides of the pan. Transfer to a cool bowl and whisk in the eggs one at a time until completely incorporated and glossy. You might want to use a hand mixer for this. Spoon the mixture to a piping bag.
Pipe small blobs of the pastry about 2cm across onto a baking paper lined tray, leaving room for the profiteroles to expand in the oven. Continue until you have 60 profiteroles.
Bake for 15-16 minutes until they have risen, turned golden and are crisp on the outside and cooked through. Allow to cool.
Heat the milk in a pan to a boil. Beat the egg yolks for the pastry cream with the sugar and vanilla in a bowl. Whisk the flour and cornflour into the egg mixture. Remove the milk from the heat and pour over the egg mixture, whisking continuously. Return the custard to the pan and gently cook until it thickens and is not at all runny, unlike crème anglaise this can bubble and boil since the flour stabilises it. Transfer the pastry cream in the fridge to cool, then fill a piping bag.
Poke a small hole into the flat bottom of each profiterole and pipe the cooled pastry cream inside.
Heat the caster sugar and water up in a pan until it starts to turn an amber colour, taking it off the heat before the colour becomes too dark. Do not stir, but swill the pan occasionally. Take each profiterole and carefully, with tongs, dip the rounded side into the caramel.
Arrange the profiteroles, one at a time, in a circle around the inside rim of a serving plate until you have a complete ring, each time allowing the dripping caramel to stick it to the plate and making sure the sugar coated rounded top is facing out.
Use the following profiteroles to stick to the layer below, slowing closing in to narrow the column. Keep repeating with a total of about 60 profiteroles, sticking each to the one below it. The higher the tower becomes the narrower it gets at the top until they meet in the middle. Keep the caramel in the pan warm by placing it back on the heat every so often. Drizzle the entire tower with extra sugar, flicking from a height to that long whisky sugar strands form.
Serve as the center piece for everybody to crack into.