Keto Citrus Custard(Posset)

Keto citrus custard posset

Keto citrus custard is a rich and creamy low carb posset.  Made with only three basic ingredients and thickened without the need for eggs or cornstarch it’s lemony treat you’re sure to make often. 

A posset is basically a cross between a rich custard and silky lemon curd. This easy keto lemon posset has a velvety smooth mousse-like texture and a bright lemon flavor.

Topping it with your favorite fresh berries makes for a perfect refreshing dessert. It’s the easiest way to make a low carb keto-friendly custard.  What’s more, this is a great make ahead keto lemon dessert, it’s why it’s perfect treat all summer long. 

Up until the other day I had no idea what a posset was. Frankly, the name didn’t sound very appealing. Come to find out that it’s a rich British citrus custard dessert. One that has been enjoyed for many centuries.

Hmmm, could this odd sounding dessert become a keto lemon custard? I, of course, had to find out. After all, converting classic recipes into keto friendly options is something I am pretty passionate about.

Let’s just say I became very curious when I realized that you only need a handful of ingredients to create a rich creamy custard. What’s more, there was no need for traditional thickeners like eggs or custard.

Just these two things reassured me that a keto citrus posset was probably very possible.

Keto Citrus Custard

Keto Citrus Custard
Keto Citrus Custard

The whole thing sounded pretty amazing and I got over the strange name rather quickly once I started to research the recipe a little deeper.

But how did the posset not need any thickeners to make the custard? I mean it doesn’t even use egg yolks! Well, it seems that it’s just a little basic science at work.

In my quest to see if I could truly convert a classic posset into a keto citrus posset I came across Cook’s Illustrated’s article.

I love how they shared their process of making this classic favorite and explained beautifully the science behind its success.

Keto Lemon Custard 

If you are a fan of lemon instant pudding, this is basically a keto lemon custard. Only it’s significantly lower in carbs and uses no preservatives. 

What’s more, the fact that it does not use any eggs makes it a great option for individuals who are allergic to eggs and want a custard dessert. 

Here is an excerpt from Cook’s Illustrated  The article does an amazing job explaining the science at work.

Cook’s Illustrated: When acid is added to milk (or when milk turns sour over time), the change in pH causes the milk’s casein proteins to lose the negative charge that ordinarily keeps them separate.

Instead, they bond together in clusters, and the milk becomes grainy, or curdled. When acid is added to cream—which is a more viscous liquid than milk, thanks to its smaller amount of water and greater amount of fat (at least 36 percent fat as opposed to whole milk’s 3.25 percent)—the effect is different.

The fat in cream outweighs the casein proteins 10 to 1 (in milk they are about equal) and so interferes with the proteins’ ability to form tight curds.

As a result, a smooth, creamy consistency develops instead of a grainy one. Heating the cream for posset also has an effect: It causes the whey proteins in the dairy to unwind and attach themselves to the casein molecules and so helps stabilize the gelled liquid.

Didn’t I tell you that Cook’s Illustrated did a marvelous job explaining the science behind this classic dessert?

Transforming Posset (Custard) Into A Keto Option

When I realized that keto citrus custard (posset) uses heavy whipping cream rather than milk for the custard, I instinctively felt that a keto option was not only possible but about to step into my life and make things just a little more magical.

The basis of this type of custard is very simple. Just heat the heavy whipping cream and sugar (in our case sugar-substitute) until it lightly boils and allows the sugar (sugar sub) to completely dissolve.

Once the mixture reduces you can add your citrus of choice and allow the mixture to congeal into a velvety smooth keto citrus custard masterpiece.

Most of the posset recipes I saw used lemon juice. You can basically use any form of citrus that is sour enough. So true to my nature I thought I would experiment by using a combination of three citrus flavors.

I knew in order to make a great keto citrus custard posset I would have to get the cream, citrus juice and sugar substitute ratios perfect.

Allowing the cream and sugar substitute to reduce sufficiently before adding the citrus juice would also prove to be vital to the success of converting posset to be keto-friendly.

Love the flavor of citrus? Perhaps you would also enjoy my Keto Lemon Curd recipe and my Keto Lemon Cookies

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All I can say is that my experimenting in the kitchen paid off. As a result of my willingness to keep converting classic recipes to fit into the life of those who adhere to a low carb keto diet, a keto custard was birthed.

I sure hope you give this simple yet delicious recipe a try and share with me your thoughts.

How about you, had you ever heard of posset? If so, share with us your first memory of having had it and if you are excited to have a keto option.

Keto Hack To Stay On Track!

TruBrain Ketone esters

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The main difference is that when supplementing with either ketone salts or ketone esters is that your body can use the energy they provide immediately. Whereas with MCT Oil your body must first break down the fatty acids before it can use it as fuel. 

By creating a ketone supplement that uses both esters and salts TruBrain has been able to address the two limitations that made it impossible for the average person to experience the use of ketone esters.

First, the cost has been dramatically reduced making it possible for more people to afford a supplement that has ketone esters and second the flavor is no longer an issue.

Their science team was able to engineer an ideal mix of both raw ketone ester plus ketones that are bound to minerals like potassium, calcium, magnesium, and sodium. 

Doing so has created a supplement that gives you the uptake of ketones so that they can experience quicker while also giving you benefits of being in a state of ketosis for a longer window. Plus the minerals in the product ensures that you are getting the proper electrolytes while supplementing with ketones. 

Enjoy the benefits of ketosis without the painful discipline required to be in nutritional ketosis. Supplementing with Trubrain ketones is a great solution for those who want to do a keto diet but find it hard to stay in ketosis or who simply want to raise their threshold of carb allowance.

Although supplementing with ketones does not automatically equate to weight loss it can be a tool in your weight loss goals. Mainly because exogenous ketones act as a strong appetite suppressor. 

TruBrain has made it easy for you to try their products by offering our readers a 20% discount. Simply use our code: FITTOSERVE at checkout

For more information about Trubrain, I invite you to read my full review on Trubrain ketone esters.

Keto citrus custard posset

Keto Citrus Custard

Yield: 4
Prep Time: 10 minutes
Cook Time: 6 hours
Total Time: 6 hours 10 minutes

A Keto citrus custard- It's a posset recipe. This recipr is the a great low carb keto-friendly option for the classic British custard recipe called posset.


Keto Citrus Custard

  • 2 ½ cups of heavy whipping cream
  • 1/2 cup of sugar substitute (I used Swerve)
  • 4 tablespoons of lemon juice
  • 2 tablespoons of lime juice
  • ½ teaspoon of orange extract
  • Dash of sea salt


  • 1 teaspoon of grated lemon rind
  • 1 teaspoon of grated lime rind
  • 1/2 cup of fresh blueberries


  1. Boil the heavy cream and sugar substitute for 6 minutes. Stirring to make sure the mixture does not boil over.
  2. Take the cream mixture off the stove and add the citrus juice, orange extract, and sea salt and mix well.
  3. Pour the keto posset into four 1/2 cup ramekins.
  4. Chill for at least 6 hours or overnight to allow mixture to fully congeal.


  1. Top with lemon and lime rind and fresh blueberries.
Nutrition Information:
Yield: 4 Serving Size: 1/2 cup
Amount Per Serving: Calories: 264Total Fat: 27.9gSaturated Fat: 17.5gCholesterol: 103mgSodium: 33mgCarbohydrates: 2.6gFiber: .1gSugar: .6gProtein: 1.7g

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