Catherine Adams prefers to use weight measurements for all ingredients, which is usual practice for pastry chefs. You'll need four wine corks cut with a serrated knife to 3cm for this recipe. To serve the millefeuille, carefully slice portions at 5cm intervals using a serrated knife.
This dessert is all about great puff pastry and crème pâtissière - a combination that just works so well. French for a thousand leaves, the millefeuille usually consists of three layers of puff pastry sandwiched together with some form of cream. Because the puff pastry is so important it's best to make your own; otherwise buy an all-butter puff pastry such as Carême. In summer, bear in mind that puff is harder to work with on a hot day, so you need to work quickly, and if it gets too warm, cool it in the fridge and keep any pieces you're not working with in the fridge, too. A level piece of stone or marble to roll it out on helps because it keeps cool.
The top and bottom layers of pastry, the puffy layers that create the thousand-leaf effect, are made slightly thicker than the third. This I roll smaller and thinner, and I dust it in sugar to make a crisp caramelised centre layer to add crunch.
To ensure the thicker pieces rise to an even height, I cut four corks down to the same thickness I want the pastry and place them in the corners of a baking tray and put another tray on top to stop it rising beyond that height.
The oven needs to be hot at first (210C) to get the initial "puff"; if it's not hot enough the butter starts to melt out of the pastry before it cooks properly. After that, reduce the temperature (to about 190C) so the pastry cooks through to the centre without getting too dark on top. If it starts to darken too quickly, reduce the temperature a little more.
I cook the sugared piece of pastry for the centre at a slightly lower temperature so the sugar doesn't burn (about 180C). It also starts in a hot oven so the butter starts to cook the pastry layers, but you don't want it to get crisp yet; I later place a tray on top to weight the pastry down which helps to caramelise the sugar. Turn the pastry once to ensure it cooks evenly - use an oven mitt for this.
The pastry can be made a day ahead and keeps well in an airtight container. If the humidity has softened it slightly, refresh it in a hot oven (180C) for three to five minutes, but cool it before assembling the millefeuille.
The pastry cream, meanwhile, is very versatile and can be made a couple of days ahead. As it heats, I stir it with a wooden spoon, scraping the base of the pot (if it gets lumpy, use a whisk to break down the lumps). Maintain the temperature at just below boiling to allow the starches to absorb as much liquid as they can.
Crème pâtissière folded with thickly whipped cream works in small millefeuilles, but for a large one I add a little gelatine to make it more stable. Once it's cooked, cover it directly with plastic wrap to prevent a skin forming and refrigerate it until it's chilled and firm; then you can fold in chilled whipped cream to loosen and aerate the texture. Return it to the fridge in a piping bag to firm up again (for about 40 minutes). You can flavour the cream with nut pastes, such as hazelnut or chestnut, pieces of praline or even a splash of liqueur (if you add more liquid, you may need to increase the gelatine).
To assemble the millefeuille, trim the pastry edges for presentation (though it's not necessary) and pipe the pastry cream between the three layers and place it in the fridge for a good 30-40 minutes to set the cream. You can assemble it up to four hours ahead, but take it out of the fridge about 30 minutes before serving to take the chill off the pastry.
For a contrast with the buttery pastry and cream, serve it with something on the tangy side, but not high acid. Berries are great, or stone fruit, but stay away from citrus and pineapples. And a dusting of icing sugar gives it that extra Christmas appeal.