Ripe for a refreshing dessert that requires no baking? This key lime mousse delivers a bright, citrus flavor with a cloud-like texture. It’s an elegant yet simple treat perfect for warm days or when you crave something light and tangy.
Why This Recipe Works
- Uses both fresh lime juice and zest for maximum citrus flavor without artificial taste.
- Heavy cream whipped to stiff peaks creates a stable, airy base that holds its shape for hours.
- Sweetened condensed milk adds sweetness and a smooth, creamy texture without requiring cooking.
- Chilling for at least 4 hours allows flavors to meld and the mousse to set properly.
- Simple assembly with minimal equipment makes this accessible for all skill levels.
Ingredients
- 2 cups heavy whipping cream (cold)
- 1 (14-ounce) can sweetened condensed milk (chilled)
- 1/2 cup freshly squeezed key lime juice (from about 12-15 key limes, or use regular lime juice)
- 2 tablespoons finely grated key lime zest (from about 4-5 key limes)
- 1/4 cup powdered sugar
- 1 teaspoon pure vanilla extract
- 1/4 teaspoon salt
- Graham cracker crumbs or fresh lime slices for garnish (optional)
Equipment Needed
- Stand mixer or hand mixer with whisk attachment
- Large mixing bowl (chilled if possible)
- Medium mixing bowl
- Measuring cups and spoons
- Microplane or fine grater for zesting
- Citrus juicer or reamer
- Rubber spatula
- 6-8 serving glasses or one large serving dish
Instructions
Step 1: Prepare the Lime Components
Begin by washing 4-5 key limes thoroughly under cool running water to remove any surface residue. Pat them dry with a clean kitchen towel. Using a microplane or the finest side of a box grater, carefully remove the bright green outer zest from the limes, avoiding the bitter white pith beneath. You need 2 tablespoons of finely grated zest. Set this aside in a small bowl. Next, cut the zested limes in half crosswise. Use a citrus juicer or reamer to extract all the juice from each half, straining it through a fine-mesh sieve to catch any seeds or pulp. Measure out exactly 1/2 cup of juice. If you’re short, juice additional limes until you reach the required amount. The combination of fresh zest and juice provides the authentic, vibrant lime flavor that defines this dessert. Tip: Roll the limes firmly on your countertop before cutting to help release more juice.
Step 2: Whip the Cream to Stiff Peaks
Pour 2 cups of cold heavy whipping cream into the bowl of a stand mixer fitted with the whisk attachment, or into a large mixing bowl if using a hand mixer. Ensure both the cream and the bowl are well-chilled—this helps the cream whip faster and achieve greater volume. Start mixing on medium-low speed for about 30 seconds to incorporate air, then increase to medium-high. As the cream begins to thicken, gradually add 1/4 cup of powdered sugar through a sifter to prevent lumps. Continue whipping until the cream forms stiff peaks, which typically takes 3-4 minutes total. To test, lift the whisk; the cream should stand straight up without drooping. Be careful not to over-whip, as this can turn the cream grainy and eventually into butter. Once done, set the whipped cream aside temporarily.
Step 3: Combine the Lime Mixture
In a separate medium mixing bowl, pour the entire 14-ounce can of chilled sweetened condensed milk. Add the 1/2 cup of freshly squeezed key lime juice, 2 tablespoons of the reserved lime zest, 1 teaspoon of pure vanilla extract, and 1/4 teaspoon of salt. Use a whisk to blend these ingredients together thoroughly for about 1-2 minutes until the mixture is smooth and uniform. The acid from the lime juice will slightly thicken the condensed milk, creating a tangy base. At this stage, taste the mixture; it should be boldly citrusy and sweet, as the whipped cream will dilute the flavor slightly later. Tip: If you prefer a less tart mousse, reduce the lime juice to 1/3 cup, but note this may affect the setting ability.
Step 4: Fold the Components Together
Using a large rubber spatula, add about one-third of the whipped cream to the lime mixture. Gently fold it in by cutting down through the center, sliding the spatula along the bottom of the bowl, and lifting up over the top. Rotate the bowl a quarter turn with each fold. This initial incorporation lightens the lime mixture. Once combined, pour the lightened lime mixture into the bowl with the remaining two-thirds of the whipped cream. Continue folding gently but decisively until no white streaks remain and the mousse is uniformly pale green. This should take about 15-20 folds. Avoid stirring or beating, as aggressive mixing will deflate the air bubbles in the whipped cream, resulting in a denser mousse.
Step 5: Chill and Serve
Divide the mousse evenly among 6-8 individual serving glasses or spoon it into one large serving dish. Smooth the tops with the back of a spoon. Cover the glasses or dish tightly with plastic wrap, ensuring the wrap touches the surface of the mousse to prevent a skin from forming. Refrigerate for a minimum of 4 hours, though overnight is ideal for the best texture and flavor development. The mousse will firm up slightly as it chills. When ready to serve, garnish with a sprinkle of graham cracker crumbs or a thin lime slice if desired. Serve cold. Tip: For optimal presentation, chill the serving glasses in the freezer for 15 minutes before filling.
Tips and Tricks
For the smoothest zest, use a microplane and only grate the green part of the lime skin. If you don’t have key limes, regular Persian limes work well; use 3-4 for juice and zest. To ensure your whipped cream reaches stiff peaks, chill your mixing bowl and beaters in the freezer for 10-15 minutes before starting. If your mousse seems too soft after chilling, it may need more time; refrigerate for another 1-2 hours. For a dairy-free version, use full-fat coconut cream instead of heavy whipping cream and sweetened condensed coconut milk. When folding, use a spatula with a flexible edge to maintain the mousse’s airy texture. Store leftovers covered in the refrigerator for up to 3 days; it may soften slightly but remains tasty.
Recipe Variations
- Add 1/2 cup of crushed graham crackers or vanilla wafer crumbs layered between the mousse for a textural contrast reminiscent of key lime pie.
- Incorporate 1/2 cup of fresh raspberries or strawberries, lightly mashed and folded in at the end, for a berry-lime twist.
- Replace the vanilla extract with 1/2 teaspoon of coconut extract and top with toasted coconut flakes for a tropical flavor.
- For a richer version, fold in 4 ounces of softened cream cheese blended with 2 tablespoons of sugar into the lime mixture before adding whipped cream.
- Make it boozy by adding 2 tablespoons of white rum or tequila to the lime mixture, adjusting for a subtle adult twist.
Frequently Asked Questions
Can I use bottled lime juice instead of fresh? Fresh juice is recommended for the best flavor, as bottled juice often contains preservatives and lacks brightness. If necessary, use high-quality bottled key lime juice, but expect a slightly less vibrant taste. Fresh zest is non-negotiable for authentic citrus aroma.
How do I know when the cream is whipped to stiff peaks? The cream will hold its shape firmly when the whisk is lifted, forming peaks that stand straight up without curling over. It should look smooth and glossy, not grainy. Under-whipped cream will result in a runny mousse, while over-whipped cream becomes buttery.
Can I make this mousse ahead of time? Yes, it’s ideal for making ahead. Prepare it up to 24 hours in advance, cover, and refrigerate. The flavors improve with time. For longer storage, freeze in an airtight container for up to 1 month; thaw in the refrigerator before serving.
Why did my mousse not set properly? This usually happens if the cream was under-whipped, the lime juice was reduced too much, or chilling time was insufficient. Ensure cream reaches stiff peaks, use the full 1/2 cup of juice, and chill for at least 4 hours. Warm ingredients can also prevent setting.
Is there a low-sugar alternative? For less sugar, use reduced-fat sweetened condensed milk or a sugar-free version, though texture may be slightly thinner. Avoid substituting the condensed milk entirely, as it provides necessary sweetness and structure; alternatives like milk won’t work well.
Summary
This key lime mousse combines whipped cream, sweetened condensed milk, and fresh lime for a light, tangy dessert. It requires no cooking, sets in the fridge, and offers a refreshing finish to any meal.
