Dietary guidance: v
For the choux buns:
2½ oz (60 g) strong plain flour
1 level teaspoon caster sugar
2 oz (50 g) butter, cut into small pieces
2 large eggs, well beaten
For the filling:
1 x 250 g tub mascarpone
½ x 350 ml pot fresh custard
1 teaspoon vanilla extract
For the caramel:
4 oz (110 g) granulated sugar
Pre-heat the oven to gas mark 6, 400°F (200°C).
You will also need a solid baking sheet, lightly greased, and greaseproof paper.
First of all, as you are going to need to 'shoot' the flour quickly into the water and melted butter, fold a sheet of greaseproof paper to make a crease, then open it up again. Sift the flour straight on to the square of greaseproof and add the sugar.
Next, put 5 fl oz (150 ml) of cold water in a medium-sized saucepan together with the pieces of butter, then place the saucepan over a moderate heat and stir with a wooden spoon. As soon as the butter has melted and the mixture comes up to the boil, turn off the heat immediately as too much boiling will evaporate some of the water. Then tip the flour in â€“ all in one go â€“ with one hand, while you beat the mixture vigorously with the other. You can do this with a wooden spoon, though an electric hand whisk will save you lots of energy.
Beat until you have a smooth ball of paste that has left the sides of the saucepan clean â€“ probably this will take less than a minute. Then beat the beaten eggs in â€“ a little at a time, mixing each addition in thoroughly before adding the next â€“ until you have a smooth, glossy paste.
At this stage, hold the greased baking sheet under cold running water for a few seconds, and tap it sharply to get rid of excess moisture. This will help create a steamier atmosphere, which in turn helps the pastry to rise.
To make the choux buns, place teaspoons of choux pastry on the baking sheet, leaving 1 inch (2.5 cm) between them, then bake on a high shelf in the pre-heated oven for 10 minutes. After that, increase the heat to gas mark 7, 425°F (220°C), and bake for a further 15-20 minutes until the choux buns are crisp, light and a rich golden colour. Pierce the side of each one to let out the steam, then cool them on a wire rack.
Make the mascarpone cream â€“ whisk together the mascarpone and the fresh custard then beat in the vanilla extract. Just before serving, split the choux buns in half and fill each one with a teaspoon of the mascarpone cream, then join the halves together again.
Next, make the caramel. Melt the sugar in a medium saucepan over a very gentle heat. To get all the sugar to dissolve, just shake and tilt the pan from side to side but don't stir. When all the sugar has dissolved, and you have a clear syrup of a golden caramel colour, remove the pan from the heat.
Dip the buns in the caramel (take care with the caramel as it will be extremely hot) and arrange them on a cake stand or plate in a pyramid shape. The caramel will help them stick together. If the caramel starts to set before the croquembouche is assembled, place it back over a gentle heat. Drizzle any remaining caramel over the pyramid and down the sides. Be careful when serving, as the caramel shatters easily!