Keto lemon mousse is impossibly light and airy, with a velvety lemon curd base folded into softly whipped cream. Mascarpone and sour cream give it richness while fresh lemon zest keeps it bright. Chill for 30 minutes and serve it in glasses.
If you’re a fan of desserts that taste like sunshine in a spoon, you’ve come to the right place. I absolutely adore the bright, zesty punch of fresh lemon, and this mousse captures it perfectly. It’s the ultimate palate cleanser—impossibly light and airy, yet with a rich, velvety texture that feels incredibly decadent. Each spoonful is a perfect balance of sweet and tart, making it a sophisticated dessert that’s surprisingly simple to whip up. Whether you’re finishing a heavy meal or just need a refreshing treat, this lemon mousse is pure bliss.
Ingredients
• For the Lemon Curd Base
• 2/3 cup / 133 g (4.7 oz) granular erythritol
• 1 tablespoon / 6 g (0.21 oz) grated lemon zest, plus extra for garnish
• 1/3 cup / 80 ml fresh lemon juice
• 2 large egg yolks
• ½ cup / 113 g (4 oz) mascarpone cheese, softened
• ½ cup / 120 g (4.2 oz) full-fat sour cream
• For the Whipped Cream
• 1 cup / 240 ml heavy cream, very cold
• 1 tablespoon / 10 g (0.35 oz) powdered erythritol
• ½ teaspoon / 2.5 ml (0.1 fl oz) pure vanilla extract
• For Garnish (Optional)
• Slivered almonds
• Fresh mint leaves
Instructions
1. Create a double boiler by setting a heatproof bowl over a saucepan with about an inch of simmering water. Ensure the bottom of the bowl does not touch the water.
2. In the heatproof bowl, whisk together the granular erythritol, lemon zest, lemon juice, and egg yolks. Continue whisking constantly over the simmering water for about 6 minutes, until the sweetener has fully dissolved and the mixture has thickened enough to coat the back of a spoon.
3. Remove the bowl from the heat and allow the lemon mixture to cool for 5-10 minutes. Whisk in the softened mascarpone and sour cream until smooth. Place the bowl in the refrigerator to chill while you prepare the whipped cream.
4. To make the whipped cream, combine the cold heavy cream, powdered erythritol, and vanilla extract in a large mixing bowl. Using an electric mixer, beat on high speed until light, fluffy, stiff peaks form.
5. Gently fold 1½ cups of the finished whipped cream into the chilled lemon mixture until just combined. Be careful not to overmix, as this will deflate the mousse.
6. Spoon the lemon mousse evenly into 6 serving glasses or ramekins. Top with the remaining whipped cream, a sprinkle of extra lemon zest, and garnish with slivered almonds and fresh mint, if desired. Chill for at least 30 minutes before serving.
Nutritional Information
• Nutrition Information
• Serving Size: 1
• Calories: 240
• Fat: 24 g
• Protein: 3 g
• Total Carbs: 3.3 g (0.12 oz)
• Dietary Fiber: 0.2 g
• Net Carbs: 3.1 g (0.11 oz)
• Erythritol: 25 g (0.88 oz)
Pro Tips
• For the fluffiest whipped cream, chill your mixing bowl and beaters in the freezer for 15 minutes before you begin.
• Use room temperature mascarpone and sour cream to ensure they blend seamlessly into the lemon curd base without any lumps.
• When combining the whipped cream and lemon base, use a gentle folding motion with a spatula. Cut down the middle, scrape along the bottom, and ‘fold’ it over. This preserves the airy texture.
• The zest of the lemon contains essential oils that provide the strongest lemon flavor. Don’t press too hard when zesting to avoid the bitter white pith underneath.
FAQ
Q: Can I use regular sugar instead of erythritol
A: This recipe is specifically designed to be low-carb and keto-friendly using erythritol. While you can likely substitute regular granular and powdered sugar in a 1:1 ratio, it will significantly change the nutritional information and it will no longer be a sugar-free dessert.
Q: Why isn’t my lemon mousse light and airy
A: For the fluffiest texture, ensure your heavy cream is very cold and that you beat it to stiff peaks. The most crucial step is to gently fold the whipped cream into the lemon base. Overmixing will deflate the air bubbles, resulting in a denser mousse.
Q: Can I make this lemon mousse ahead of time
A: Absolutely. This dessert is perfect for making ahead. You can prepare the mousse and keep it chilled in individual serving glasses for up to 2 days. We recommend adding any garnishes like fresh mint or almonds just before serving for the best texture and appearance.
Q: Is there a substitute for mascarpone cheese
A: Yes, if you don’t have mascarpone, you can substitute it with an equal amount of full-fat cream cheese. Make sure the cream cheese is softened to room temperature to ensure it blends smoothly into the lemon curd base without lumps.
Pro Tips
- Chill the mixing bowl and beaters in the freezer for 15 minutes first — the cream whips fluffier when everything is cold.
- Keep the mascarpone and sour cream at room temperature so they blend into the lemon curd without lumps.
- Zest lightly: the yellow peel holds the lemon oils, while pressing too hard scrapes bitter white pith into the curd.
- Fold the whipped cream with a cut-down-the-middle, scoop-the-bottom, fold-over motion and stop early — overmixing deflates the mousse.
- Whisk the curd constantly over simmering water for about 6 minutes until it thickens enough to coat the back of a spoon.
Frequently Asked Questions
Is lemon mousse keto?
Yes: each serving has 3.3 g of total carbs and 0.2 g of fiber (3.1 g net), with 24 g of fat; all the sweetness comes from erythritol.
How far ahead can I make it?
Chill it at least 30 minutes before serving; it also holds beautifully overnight in the refrigerator.
Can I use bottled lemon juice?
Fresh juice and zest are the whole flavor here — bottled juice tastes flat next to the rich mascarpone base.
How do I keep the mousse from deflating?
Fold the whipped cream in gently and stop the moment it is combined; stirring knocks the air out.
Recipe card below.
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Keto Lemon Mousse
Ingredients
Method
- Create a double boiler by setting a heatproof bowl over a saucepan with about an inch of simmering water. Ensure the bottom of the bowl does not touch the water.
- In the heatproof bowl, whisk together the granular erythritol, lemon zest, lemon juice, and egg yolks.
- Continue whisking constantly over the simmering water for about 6 minutes, until the sweetener has fully dissolved and the mixture has thickened enough to coat the back of a spoon.
- Remove the bowl from the heat and allow the lemon mixture to cool for 5-10 minutes.
- Whisk in the softened mascarpone and sour cream until smooth.
- Place the bowl in the refrigerator to chill while you prepare the whipped cream.
- To make the whipped cream, combine the cold heavy cream, powdered erythritol, and vanilla extract in a large mixing bowl.
- Using an electric mixer, beat on high speed until light, fluffy, stiff peaks form.
- Gently fold 1½ cups of the finished whipped cream into the chilled lemon mixture until just combined. Be careful not to overmix, as this will deflate the mousse.
- Spoon the lemon mousse evenly into 6 serving glasses or ramekins.
- Top with the remaining whipped cream, a sprinkle of extra lemon zest, and garnish with slivered almonds and fresh mint, if desired.
- Chill for at least 30 minutes before serving.
- When combining the whipped cream and lemon base, use a gentle folding motion with a spatula.
- Cut down the middle, scrape along the bottom, and 'fold' it over. This preserves the airy texture.
