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.

Classic Posset

IngredientQuantity%
Heavy Cream540 grams70
Sugar150 grams20
Lemon Juice75 grams10
  1. Bring cream and sugar to boil over medium-high heat, stirring until sugar dissolves.
  2. Boil 3 minutes, stirring constantly, adjusting heat as needed to prevent mixture from boiling over. Remove from heat.
  3. Stir in lemon juice and cool 10 minutes.
  4. Stir mixture again and divide among six 1/2-cup ramekins or pour into a baked 9″ tart shell.
  5. Cover and chill possets until set, at least 4 hours or overnight.

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!

Playing Around

Swap out the lemon juice for another juice

When swapping juices, you’ll need to take acidity into account. Lemon juice is very acidic, which is crucial to the setting of a posset. When considering switching to a different juice, take a look at this handy chart to see where the juice falls on the pH scale.

If juice pH is..then do this
3.0 or lower1. Replace 100% of the lemon juice with new juice
For example, I’ve successfully done this with lime juice (pH 2.2)
Between 3.0 and 3.51. Replace 50% of the lemon juice with new juice
For example, I’ve done this with grapefruit juice (pH 3.1)
Above 3.51. Replace no more than 25% of the lemon juice with new juice
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 less acidity

Swap out cream for another liquid

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

Add spices or herbs

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.

To add flavors through steeping:

  1. Place the cream in a small pot or microwave-safe container. Warm the cream until steaming.
  2. Remove the cream from heat and add your chosen steeping ingredients. Some ideas:
    • 1 tablespoon of loose leaf Earl Grey tea
    • 2 tablespoons dried, loose leaf hibiscus flowers
    • 2 cinnamon sticks
    • 1 lightly crushed cardamom pod
  3. Cover the container and let the cream sit at room temperature for about 30 minutes. Depending on the strength of your steeping ingredient, you may need to use more or less time. Use your nose as a guide! Once the cream has taken on the smell or color of your chosen ingredient, proceed to step 4.
  4. Place a fine mesh sieve over a pot. Pour the cream over the strainer. Use a spoon or spatula to gently press on the steeping ingredients, extracting the last bits of flavor/color.
  5. Reweigh the cream. You may have lost some of the original amount due to absorption. Add back fresh cream until you reach the initial weight.
  6. Proceed with the basic posset recipe as above.

Make a Posset Tart

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!

Variations

If you want to make a posset with some fun flavors but don’t feel like doing the brainstorming/math portions, here are some variations that I love!

Strawberry Lemonade

IngredientQuantity
Heavy Cream540 grams
Roasted Strawberry Puree20 grams
Sugar150 grams
Lemon Juice55 grams

  1. To make roasted strawberry puree:
    • Roast 50 grams of halved strawberries with 20 grams of sugar at 325F until jammy, about 20 minutes
    • Puree and press though a mesh strainer to remove the seeds
  2. Combine the heavy cream, strawberry puree, and sugar in a pot.
  3. Bring the strawberry cream and sugar to boil over medium-high heat, stirring until sugar dissolves.
  4. Boil 5 minutes, stirring constantly, adjusting heat as needed to prevent mixture from boiling over. Remove from heat.
  5. Stir in lemon juice and cool 10 minutes.
  6. Stir mixture again and divide among six 1/2-cup ramekins or pour into a baked 9″ tart shell.
  7. Cover and chill possets until set, at least 4 hours or overnight.

Green Apple

IngredientQuantity
Heavy Cream540 grams
Green Apple Juice20 grams
Sugar150 grams
Lemon Juice55 grams
  1. To make green apple juice:
    • Slice and puree one raw green apple
    • Press through a fine mesh strainer to remove any solids
  2. Combine the heavy cream, apple juice, and sugar in a pot.
  3. Bring the apple, cream and sugar to boil over medium-high heat, stirring until sugar dissolves.
  4. Boil 5 minutes, stirring constantly, adjusting heat as needed to prevent mixture from boiling over. Remove from heat.
  5. Stir in lemon juice and cool 10 minutes.
  6. Stir mixture again and divide among six 1/2-cup ramekins or pour into a baked 9″ tart shell.
  7. Cover and chill possets until set, at least 4 hours or overnight.



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