Posset – The old school dessert we’re bringing back

I have a thing for fillings. That’s a weird thing to say, but I just love the science behind the different flavors and textures of anything that could fill a tart shell: ganache, lemon curd, pastry cream, curd – all those good guys. Because I love fillings so much, I’ve recently gotten obsessed with posset. It’s a 3 ingredient custard that tastes like the love child of lemon curd & pastry cream. Need I say more? (Just kidding – I’m going to say a lot more!)

Let’s talk about a basic posset first! It can be adapted in lots of different ways, but it’s important to understand the basic science first so you know which boundaries can be pushed.

The Science

Now that you understand how a basic posset comes together, we can talk about why these three components work together so beautifully!

• Dissolving sugar into cream keeps the posset from being gritty
• Sugar adds sweetness (no surprises there)
• Boiling the cream evaporates off a little bit of the water, concentrating the fats in the cream for an extra-luscious texture
• The lemon juice contributes acidity. Lemon juice has a pH of approximately 2.3, which is highly acidic!
• The acid coagulates the proteins in the cream, which causes the posset to thicken as it cool. Coagulation means that proteins are getting together and hanging out. The closer they hang, the firmer the final filling texture!

When swapping out the cream, remember that non-dairy milks don’t have the same fat quality of cream. Cream contributes wonderful saturated fats that coagulate beautifully when stirred with acid (this is the same general process that allows us to have cheese, albeit with different acids).

The only fat substitution I’m comfortable recommending is a portion full-fat coconut milk, since it also contains saturated fats.

To add some coconut milk:

1. Replace 25% of the heavy cream with well-stirred, full fat coconut milk
2. Boil the cream/sugar mixture for 5 minutes instead of 3 to remove a little extra water, ensuring that you’ll get a solidly set custard even with different fats

Here’s a fun food science fact – fat carries flavor! This is why steeping things in cream is such a wonderful way to add flavors to a dairy-based dessert. Adding spices, herbs, or tea blends to posset is a great way to easily change up the flavors.

Posset works beautifully as a creamy tart filling. To make a posset tart, you’ll need to do the following:

1. Make a tart shell. Fully bake the tart shell and let cool completely.
2. Make your posset as instructed in the above/below recipes.
   • The quantities listed in the recipes on this page are enough to fill one shallow 9″ tart shell.
3. Let the posset filling cool slightly in the pot, until it’s warm but not steaming.
   • Clear enough room on a refrigerator shelf to place a baking sheet! You’ll be glad you did this now and not when you’re juggling a sloshy tart.
4. Place the tart shell on a baking sheet.
5. Pour the posset filling into the tart shell. If any bubbles appear, pop them with a skewer or toothpick.
6. Carefully transfer the tart into the refrigerator.
7. Let chill for at least 8 hours to set fully.
8. Top with fruit, sauces, or anything else your heart desires!
   • Pro tip: to get super-sharp slices like in the photo above, wait until your tart is fully cold to slice it. Use a very sharp knife, and run the blade under hot water. Dry the blade off, and then slice into the tart. Use a definitive slice – you want to press down through the crust in one firm motion. Slide the knife out horizontally along the slice you just created (aka pull the knife back toward your chest without lifting up the blade). Repeat!