300 g pastry cream (recipe follows)
150 g very cold cream, straight from the refrigerator
For pastry cream:
50 g butter
450 g milk
1 vanilla bean, split and seeded
100 g egg yolks
160 g sugar
20 g all-purpose flour
5 g cornstarch
3 g salt
Place the butter in a food processor and set it aside.
Place the milk in a medium-sized pot with a heavy bottom. Split the vanilla bean lengthwise and use the tip of your knife to scrape the tiny black seeds from the pot. Place both the pod and the seeds in the pot with the milk. Set over medium-high heat.
When the milk comes to a boil, remove from heat and set aside, allowing the vanilla pod to infuse while you prepare the next step.
Place the egg yolks, sugar, flour, cornstarch, and salt in the bowl of a stand mixer. Whip these ingredients on high speed for 2 minutes, until the mixture is light and fluffy, and the egg yolks have turned a pale yellow. Reduce the speed to low.
Remove the vanilla pod from the pot of milk, and slowly drizzle the hot milk into the bowl. Aim for the space between the side of the bowl and the whip—this will reduce the risk of hot milk splattering on you. Set the emptied pot aside to use again. When all the milk has been added, stop the mixer, and use a rubber spatula to scrape the sides of the bowl clean. Whip on low for 30 more seconds to reincorporate the thicker batter that was on the sides.
Place a fine-mesh strainer over the reserved pot, and strain the custard into the pot.
Place the pot over medium heat, and grab a rubber spatula in one hand and a whisk in the other. Cook the custard over medium heat until it comes to a boil. While the custard is cooking, scrape the bottom of the pot with the rubber spatula, pulling the custard away from the bottom of the pot where it thickens faster. Whisk the custard to ensure it is smooth throughout the entire cooking process, but resist the urge to whisk it too aggressively. A gentle whisk allows the starches to swell with the increased heat without breaking. (If the starches break, they’ll cling together and form chains, which will result in a gummy pastry cream.)
When the pastry cream starts to boil, set a timer for 2 minutes, and cook, whisking and scraping, until the timer goes off.
After 2 minutes, immediately pour the hot pastry cream into the food processor with the butter. Pulse 3–5 times, until the butter is just incorporated and the pastry cream is smooth. (Be careful not to over-pulse: the added fat will help prevent the starches from forming gummy chains when agitated by the blade, but it can only do so much.)
Congratulations, you are now the proud parent of pastry cream! Do with it as you wish: whisk it in chocolate, cast it into a tart shell, or let it set for future use. To do this, transfer the pastry cream to a shallow vessel. (A wide-mouthed bowl or pie plate works well). Press plastic wrap directly on the surface of the pastry cream to prevent a skin from forming while it cools. The pastry cream needs to cool completely before it is used in another application. Not only will any residual heat from the warm pastry cream alter the texture of the added ingredients, but also the starches need to completely set before they can be moved about again, or they will lose their strength. Once cool, the pastry cream can be scraped out of the shallow vessel and stored in any airtight container for up to a week. The starches will begin to break down if it is held much longer, making the pastry cream leaky, so use it or lose it!
To make diplomat cream:
Place the pastry cream in a small bowl, and use a rubber spatula to manipulate it until it is smooth and pliable. Set this aside.
Place the cold cream in a medium-sized bowl, and whisk by hand until the cream thickens and tightens to medium peaks. Make sure the cream has come straight from the refrigerator, and choose a larger bowl than you think you will need. The cream will be dwarfed by the bowl but extra room will allow your hand a comfortable whipping motion. When you whip cream by hand, you will feel the cream transition from soft to firm, with each pass of the whisk tightening the cream. It’s such a small amount—it won’t take long.
When the cream is whipped to medium peaks, add half of it to the pastry cream. Fold gently until the cream just integrates itself, a trace or two still visible. Add the remaining cream, and fold even more gently, until the cream and pastry cream have become one. If you can still see white streaks of cream, you’re almost there, give it one or two more folds. The moment it appears even, stop! Continued folding will start to knock the air out of the mixture that you carefully whipped in to the cream.
Congratulations, you’ve just oh-so-delicately married whipped cream and pastry cream to become diplomat cream. Taste it, and note the grand texture: lighter than custard, richer than cream. The diplomat cream needs to be used immediately, and consumed within a day, as its perfect texture is fleeting. So get to work filling something!