Key Lime Pie Mousse

Yes. Fresh Persian limes work well and many bakers prefer them over bottled key lime juice. Fresh key limes still give the most traditional flavour but regular limes are a great easy little swap. We always recommend our readers to use fresh over bottled if you want better overall taste.

It works in a pinch but fresh juice usually tastes brighter and less artificial. Taste tests and side by side bakes tend to favour fresh juice for a cleaner more floral lime flavour. Try to use fresh organic limes for the best results.

This is because real key lime filling is naturally pale yellow. If you see a bright green dessert, it got that colour from food colouring not from the limes. Here are some natural compound's we've tried and tested to give the top jelly layer a nice mint pale green look:

A toothpick's worth of blue spirulina (a tiny pinch) when it mixes with acidity works well, However it is heat sensitive so don't add it to boiling liquid. Our favourite is 1/4 teaspoon of extra fine pandan leaf powder for it's aesthetic colour. Enough to colour 6 to 8 servings worth. Remember to sift this in to avoid specks in your top layer. The reason we like this is because it has it's own vanilla like note to it which makes it pair well with this sweet treat. We've tried using matcha powder but it always makes everything taste on the bitter side with it's strong taste so we stick to more neutral tasting compounds instead.

For classic pie the acid in lime juice thickens the egg yolks and condensed milk and gentle baking helps it hold a clean slice; using the wrong milk (like evaporated) or under-baking can keep it loose. For a mousse you need proper soft peak whipped cream and enough chill time. If you add a jelly top always be sure the mousse is cold before you pour it on.

Yes. Agar works but it sets firmer and less creamy than gelatin. Boil agar to dissolve it fully, use the right strength and expect a slightly different bite compared with gelatin.

The crumb base and mousse can be assembled a day ahead. Keep glasses covered in the fridge, add the jelly top once the mousse is cold and finish with zest right before serving. Leftovers keep well in the fridge for about two days; freeze is not ideal because the mousse can lose its silky texture.