Preheat oven to 415 F.

In a large, heavy based saucepan, heat the butter and water over medium heat until butter is melted and mixture is boiling.

Remove from the heat and beat in the flour with a wooden spoon.

Return the pot to the heat and beat until the mixture comes together into a ball and leaves the side of the pan. Remove again from the heat and let cool slightly.

Beat the mixture to release any more heat - you don't want to cook the eggs!

Add the eggs, one at a time, beating well after each addition. The mixture will be slippery at first, so just continue beating until the egg is well incorporated before adding the next.

Beat the mixture until it is thick and glossy - a wooden spoon should be able to stand up in the batter.

Spoon the mixture onto baking sheets lined with parchment paper. Make about 8 Tablespoon-sized puffs (these will be for the base of the croquembouche). Use up the rest of the batter for smaller puffs, each the size of 1 or 2 teaspoons of dough.

Bake for 20-30 minutes, depending on the size of the puffs, until golden brown and hollow sounding when the base is tapped. Let cool on a wire rack.

Put the milk and vanilla in the top of a double boiler. Heat gently over medium heat until lukewarm.

Meanwhile, in a medium bowl whisk the yolks, sugar, and flour until thick and pale.

Gradually add the warm milk to the egg mixture and whisk. Return the mixture to the double boiler and stir over medium heat until the custard boils and thickens.

Remove from the heat and pour into a medium bowl. Cover the surface of the custard with plastic wrap to prevent a skin from forming. Let custard cool completely.

When the custard is cool, whip the cream into stiff peaks and fold into the custard.

Put the cream filling mixture into a piping bag with a small nozzle. Poke a small hole (we used a chopstick) into the base of the cooled puffs, and fill with cream. Set aside.

To make the caramel, put the sugar and water in a heavy pan. Cook over medium heat until sugar dissolves, then simmer until it is golden. Remove from the heat and plunge the base of the pan into cold water.

To assemble the croquembouche, begin with the large puffs. Dip the bases in some caramel and arrange in a large circle on your serving platter, with the sides touching to form a ring. We built our croquembouche around an empty metal tea canister, but you can use with some other cone-shaped vessel; I've seen some recipes that used clean, upside-down flower pots!

Using gradually smaller puffs, build up into a cone shape.

To decorate, dip the tines of two forks into the caramel mixture and drizzle over the croquembouche to make a spun-sugar 'netting.'

Serve immediately.