We freeze chunks of watermelon on a parchment-lined baking sheet in a single layer, so that they don’t form giant, unworkable icebergs. And then we whirl them up with simple syrup, tequila, lime and a small amount of jalapeño pepper. The result is a slushy that looks an awful lot like a Misty, but tastes ever so much more sophisticated — it’s fruity sweet and delightfully tart with a lightly spicy jalapeño finish.