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Turn summer's most beloved fruit into something unexpected with this creamy, zippy treat that wonderfully balances sweet and tart flavors. This unusual combo has become my go-to surprise at warm-weather gatherings when folks are tired of the same old berry desserts.
I came up with this idea during a scorching summer when I had too much watermelon getting soft in my fridge. The watermelon-key lime pairing was such a knockout that my neighbors now beg for it at every summer get-together.
What You'll Need
- Biscoff cookies: They bring a warm, caramel-like foundation that works wonderfully with the fruit filling
- Almond meal: Adds a subtle nutty flavor and helps the crust stay intact
- Melted dark chocolate: Forms a protective layer so your crust stays crisp
- Fresh watermelon juice: Delivers natural sweetness and gorgeous pink color
- Key lime juice: Adds a zingy kick that balances the sweetness perfectly
- Sweetened condensed milk: Gives you that smooth, rich texture you want
- Cornstarch: Makes sure your watermelon filling firms up nicely
Preparation Guide
- Make Your Cookie Base:
- Crush Biscoff cookies in a food processor until they're completely ground down. Toss in almond meal and give it a quick pulse to mix. While the machine runs, slowly drizzle in melted butter for even coverage. Add melted chocolate and keep processing until everything looks like damp sand that sticks together when squeezed.
- Shape Your Crust:
- Lightly grease your pie dish so slices come out cleanly later. Push the cookie mix firmly across the bottom and up the sides of your dish, aiming for a layer about 1/4 inch thick all around. A measuring cup bottom works great to pack it down tight. Stick it in the freezer for at least 15 minutes while you work on the filling.
- Cook Down Your Watermelon:
- Set aside 3 tablespoons of watermelon juice in a separate bowl for later. Pour what's left into a pot with sugar and salt. Warm it over medium heat until it bubbles gently, letting some water evaporate and the flavor get stronger. Keep it going for exactly 5 minutes to keep that fresh watermelon taste alive.
- Mix Your Wet Ingredients:
- In a big bowl, mix condensed milk, lime juice, and eggs until smooth as silk. Slowly pour about 1 cup of the warm watermelon mix into this while whisking non-stop. This slowly warms up your eggs without turning them into scrambled eggs.
- Thicken Everything Up:
- Pour your egg mixture back into the pot with the rest of the watermelon liquid. Put it back on medium heat, whisking often so it cooks evenly. You'll notice it starting to thicken as it heats up. Mix cornstarch into that reserved watermelon juice until completely dissolved. Add this mix to your pot and keep cooking, whisking all the time until it bubbles and gets as thick as pudding.
- Finish It Off:
- Pour the hot filling right into your frozen crust. It should look glossy and smooth. Let it cool on your counter for 30 minutes before putting it in the fridge. Chill it uncovered for at least 6 hours but overnight works even better to let all those flavors mingle properly.
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The real trick to making this pie amazing is using super-ripe watermelon. I tried it once with a not-quite-ripe melon and had to add extra sugar because the flavor was so flat. The natural sweetness from a perfectly ripe watermelon creates something that fake watermelon flavor just can't touch.
Picking the Perfect Watermelon
Getting the right watermelon can make or break this dessert. Go for one with a yellowish patch where it sat on the ground growing. The outside should look more matte than shiny, and it should feel heavy when you pick it up, which means it's full of juice and properly ripened. Seedless types work best for this recipe since you won't need to strain as much.
Switch Things Up
You can easily tweak this recipe to suit your taste. Want more watermelon punch? Boil down another cup of juice until it's just 1/4 cup and fold it into some whipped cream for topping. Don't have key limes? Regular limes will work too, though the taste won't be quite as interesting. Need a dairy-free option? Swap the condensed milk for coconut cream and add an extra tablespoon of cornstarch.
Ways to Serve It
This pie tastes great on its own but gets even better with a few extras. Try adding a spoonful of lightly sweetened whipped cream with some lime zest scattered on top. For some crunch, sprinkle on some crushed freeze-dried strawberries or toss on a handful of fresh blueberries. Keep it cold until right before serving, pulling it from the fridge just 5 minutes before you cut it.
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You'll end up with a jaw-dropping dessert that's simple to put together but nobody will forget.
Frequently Asked Questions
- → Can I use normal limes instead of key limes?
Sure, regular lime juice works too, but it'll taste a bit different. Key limes have a stronger, more fragrant flavor. If you're using regular limes, maybe use a little less (around 2/3 cup) since they tend to be more sour.
- → How can I tell when the filling is thick enough?
The filling should look like pudding where your whisk leaves clear marks when you stir it. It should stick to the back of a spoon, and if you draw your finger through it, the line won't fill back in right away.
- → Can I make this ahead of time?
For sure! This dessert actually gets better after sitting in the fridge overnight. You can make it up to 2 days before you need it, but wait to put on the whipped cream and lime zest until you're ready to serve it.
- → What's the easiest way to turn watermelon into juice?
First, take out all the seeds from your watermelon chunks. Then blend them in a blender until smooth. Pour this through a fine strainer, gently pressing down to get the juice out without pushing the pulp through too.
- → Can I use other cookies for the base?
You bet! Graham crackers or ginger cookies work great instead of Biscoff. Just keep the same amount of cookies and butter so it sticks together well. The ground almonds add a nice texture, but you can just use more cookie crumbs if you don't have any.
- → How do I keep leftover slices?
Just wrap any leftover dessert loosely with plastic wrap and pop it in the fridge for up to 4 days. The crust might get a bit soft after a while, but it'll still taste great.