When watermelon is in season it's hard to resist. For some parties you need nothing more than to slice it and hand it out with paper towels for people to scarf down. However, sometimes you want something a little more refined and that's where this recipe comes in. This modernist watermelon soup recipe uses xanthan gum to help hold the soup together and is topped with a spicy pickled watermelon rind.
One of my favorite combinations to pair with watermelon is jalapeño, lime, and mint. Those ingredients go great together and each one offers its own little something that the others lack. For this chilled soup, they combine together in a sweet broth that has undertones of spice, mint, and sourness to round it out. I top it with a spicy pickled rind, a part of the watermelon typically overlooked. The rinds take a day or two to make but they will last in the refrigerator for at least a week.
I personally like the rustic look of the pureed ingredients but if you want a more refined soup you can strain it after pureeing it, though you will want to wait until after straining it to add the xanthan gum. You can also carbonate the soup using a whipping siphon if you want to add even more flair to it.
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Because they use modernist ingredients, these amounts are given in metric by weight. For more information on how to measure modernist ingredients check out this article.
Place all the ingredients in a blender or food processor. Processes until everything is broken down and the soup is nice and smooth. Store the soup in the refrigerator until ready to serve, it will keep for several days.
Trim the watermelon off the rind, leaving just a bit of the red flesh. Use a vegetable peeler to remove the tough, outer layer of green. Cut the watermelon rind into 1.5" x 0.5" (37mm x 12mm) strips.
Make a brine by combining the salt and 750 grams of water in a bowl, mixing until the salt is dissolved. Add the watermelon rind and let soak for at least 12 to 24 hours in the refrigerator. Drain the watermelon rinds and rinse off the excess brine.
Add the brown sugar, apple cider vinegar, and water to a pot. Heat over medium heat until the sugar dissolves. Add the watermelon rind and jalapeños then bring to a boil. Reduce to a simmer and cook for 5 minutes then remove from the heat and let cool.
You can store the pickled rinds in any air-tight container like mason jars or Tupperware. Let them rest for another 12 to 24 hours for the flavors to mellow before serving.
Fill a bowl or small glass with the watermelon-jalapeño soup. Top with a few mint leaves and a pickled watermelon rind.